Placental Mammal Radiation

During the Cenozoic placental mammals underwent a great adaptive radiation. Representatives of the modern orders of placental mammals appear by the early Eocene. Traditionally, paleontologists placed the origins of mammals among the now abandoned order Insectivora (which included shrews, moles, hedgehogs, golden moles, and tenrecs) based upon fossil teeth and jaws. Current molecular phylogenies constructed using data complied from multiple comparative studies of nuclear and mitochondrial DNA converge on the idea that placental mammals can be grouped into four major clades that represent superorders: Afrotheria, Xenarthra, Euarchontoglires, and Laurasiatheria (Benton, 2005, p. 324 & Kemp, 2005, pp. 225 & 226). Laurasiatheria and Euarchontoglires form a single clade named Boreoeutheria

The death of the dinosaurs at the end of the Cretaceous opened up many habitats. Placental mammals underwent an adaptive radiation, diversifying into many forms at the beginning of the Paleocene. Shrew-like insectivores, otter-like fish eaters, rabbit-like herbivores, and pig-sized rooting and browsing forms started to fill empty niches. At the beginning of the Paleocene placental mammals remained small, with very few reaching the size of a modern day sheep, but this would soon change by the Late Paleocene (Benton, 2005, p. 329). Multiple groups of placental mammals evolved into medium to large rooters and browsers. Tillodonts (order Tillodontia) evolved into bear-sized rooters and browsers. Pantodonts (order Pantodonta) evolved into sizes and forms reminiscent of pigs, hippos, and sloths. In addition to these orders and many more, an important group of archaic ungulates, the condylarths, evolved into both herbivores and carnivores.

Condylarths

Archaic ungulates know as the “Condylarths” specialized into larger herbivores and interestingly, carnivores. Modern placental ungulate orders are believed to lie within this basal group (Kemp, 2005, p. 234). Dinocerates (order Dinocerata), also known as uintatheres, were the largest mammals of the late Paleocene and early Eocene of North America and Asia. These rhinoceros-like organisms possessed bony protuberances on their skulls and males were equipped with a pair of long, sabre-like canines. Uintatheres went extinct in the Oligocene.

The largest Paleocene carnivores were the mesonychids (family Mesonychidae). Mesonychids were wolf-sized, meat-eating ungulates! Their fossil range is Paleocene to Early Oligocene. Andrewsarchus from the late Eocene of Mongolia had the largest skull of any known terrestrial carnivore at 83 cm long and 56 cm wide (Kemp, 2005, p. 333). This 5-6 m long organism probably had a hyena-type lifestyle. Mesonychids are believed to be close relatives of modern day whales. Creodonts (order Creodonta) were the main carnivores from the Paleocene to the Oligocene of North America, Europe, and Asia. Creodonts evolved into a diversity of forms ranging from weasel to bear size. Sarkastodon of the Late Eocene of Mongolia was a bear-sized carnivore. Hyaenodon of the late Eocene to early Miocene of North America, Europe, Asia, and Africa evolved into a variety of sizes. Hyaenodon horridus was a common wolf-sized scavenger during the Oligocene in North America. Hyaenodon possessed a long skull equipped with bone crushing teeth and a small brain case. Hyaenodon had short stocky legs with five toed feet that ended in hoof-like claws. Hyaenodon gigas reached small rhino size.

South American Ungulates

During the early Paleocene, South America was isolated from other continents. Four clades of unique South American ungulates evolved in isolation from other ungulate groups around the world. The four clades are clustered into the unranked group Meridiungulata. South American ungulates have a fossil record that spans from the Paleocene to the Pleistocene. During the Pleistocene South and North America once again became connected. The four clades of South American ugulates soon became extinct. These clades may have originated from a North American condylarth ancestor.

Litopterns (order Litopterna) consisted of organisms that resembled horses and camels in many ways. Diadiaphorus of the early Miocene of Argentina resembled a sheep-sized, three toed horse. Macrauchenia from the Pleistocene of Argentina resembled a hump-less camel with rhinoceros-like feet and a tapir-like trunk. Notoungulates (order Notoungulata) were by far the most diverse of the South American ungulates. Notoungulates evolved into many forms resembling such animals as rabbits, beavers, sheep, wart hogs, rhinoceroses, horses, and hippopotamuses (Palmer, 2006 p. 394). Taxodon from the Pleistocene of Argentina was the largest notoungulate. Taxodon looked somewhat like a cross between a hippopotamus and a rhinoceros. Its hind legs were longer than its fore legs, so the body sloped forwards. Its feet had three toes. Taxodon teeth grew continuously to keep up with the wear from grazing. Charles Darwin was one of the first to collect Taxodon and commented on its strangeness (Benton, 2005, p. 320). Astrapotheres (order Astrapotheria) from the Paleocene to the late Miocene possessed tusk-like canine teeth. While most were of moderate size, at least one species reached rhinoceros size. Astapotherium of the late Oligocene and middle Miocene of Argentina superficially resembled a tapir with tusk-like canines and a short trunk. This organism probably had a semi-aquatic life not unlike a hippopotamus. The pyrotheres (order Pyrotheria) were large bodied, tapir-like organisms with tusk-like incisors and trunks. Pyrotherium means fire animal and refers to the fact that the first specimens were recovered from a volcanic ash fall deposit (Palmer, 2006, p. 393). Pyrotherium was somewhat reminiscent of an elephant with pillar like legs supporting a massive body. The head contained forward pointing tusk-like incisors, two upper pairs and one lower pair. Pyrotherium also had a trunk.

The fact that South American ungulates independently evolved similar structures in response to similar environmental pressures makes them good examples of convergent evolution. Even though South America was isolated, some small placental mammal groups reached the continent and flourished. Rodents invaded during the Eocene, while bats and primates reached South America by the Oligocene (Benton, 2005, p. 320). The South American Ungulates (Meridiungulata) and the condylarths are included within the clade Laurasiatheria.

Afrotheria

The superorder Afrotheria groups aardvarks, tenrecs, golden moles, hyraxes, sea cows, and elephants. Afrotheria may have been the first group to split from the remaining placental animals around 105 Ma when Africa was separated from the rest of the continents.

Aardvarks & Golden Moles

Aardvarks (order Tubulidentata) are medium-sized burrowing nocturnal animals native to Africa that eat ants and termites. Fossil aardvarks date back to the Miocene. Tenrecs and golden moles (order Afrosoricida) date to the Miocene. Tenrecs are a diverse group of mammals that live in Madagascar and West Africa. Golden moles are small burrowing mammals that live in South Africa. Tenrecs and golden moles are insectivorous mammals and use to be grouped with Lipotyphla. Elephant shrews (order Macroscelidea) resemble shrews with a long nose. These small insectivorous mammals are native to Africa and date back to the middle Eocene.

Hyraxes & Sea Cows

Hyraxes (order Hyracoidea) are rabbit-sized vegetarians that resemble guinea pigs. Today, hyraxes live in Africa and the Middle East. Fossil hyraxes are known from the Eocene. Sea cows or manatees and dugongs (order Sirenia) are large aquatic herbivores that live in both marine and freshwater environments. In fact, sirenians are the only known group of mammals to become fully aquatic herbivores (Plamer, 2006, p. 372). Sirenians closest living relatives are the hyraxes and elephants. Pezosiren, the oldest known sirenian from the Early Eocene of Jamaica, still had short functional legs. Other skeletal features of Pezosiren indicate a primarily aquatic life (Rose, 2006, p. 269). Later forms, such as Dusisiren from the Miocene, had paddle-like forelimbs, vestigial hindlimbs (reduced and non-functional) and a whale-like tail (Benton, 2005, p. 326). Steller’s sea cow (Hydrodamalis gigas) was a large ocean dwelling sirenian that only recently became extinct. Steller’s sea cow was up to 8 m long and lived in the Arctic and North Pacific oceans. Steller’s sea cow evolved sometime during the Pleistocene and was hunted to extinction by 1768.

Elephants & Their Relatives

Proboscids (Order Proboscidea) comprise living elephants and their extinct relatives. Phosphatherium (family Numidotheriidae) is the oldest and smallest known proboscidean from the Early Eocene of Morocco. This organism was dog sized, at just over a half meter in length and weighing in at 15 kg. Moeritherium (family Moertheriidae), from the late Eocene and Early Oligocene of North Africa is another well-known early pig-sized proboscidean that stood a meter high and weighed 200 kg (Palmer 2006, p. 382). The incisors were small and tusk-like, but these early forms did not possess a trunk. In fact, the shape of their bodies would remind one of a modern day tapir. Phosphatherium and Moeritherium were amphibious browsers that fed on freshwater vegetation, not unlike a hippopotomous. Early proboscideans split into two lineages, the deinotheres and elephantiforms (gomphotheres, stegodontids, mammutids, and elephantids) sometime in the Eocene.

Deinotheres (family Deinotheriidae) are elephant-like proboscideans that range from the Miocene to the Pleistocene of Africa, Europe, and southern Asia. Deinotheres lower jaw curved backwards and was equipped with two incisor-like tusks that curled under the chin. These tusks are the most distinctive feature of this family and may have been used to scrape bark from trees (Benton, 2005, p. 326). Deinotherium was one of the largest land animals of the Miocene with males reaching 4.5 meters tall and weighing in at 11 tons.

Elephantoids underwent a great adaptive radiation during the early Miocence, which resulted in multiple groups including gomphotheres, stegodontids, and mammutids. All of these groups are now extinct. In the late Miocene another radiation resulted in the elephantids (mammoths and elephants), this family survives today (Benton, 2005, p. 327).

Gomphotheres (family Gomphotheriidae) were diverse and successful elephant-like proboscideans that range from the Miocene to Pleistocene. Gomphotheres were the dominant large mammal of the Miocene. Gomphotheres originated in Africa and migrated to Europe and the Americas. Most gomphotheres were equipped with four tusks, two upper and two lower. The lower tusks on some gomphotheres were flat and paired, giving the appearance of a shovel, hence the nickname “shovel-tuskers”. Platybelodon was a shovel-tusked browser that lived in the Late Miocene of Africa, Europe, Asia, and North America. Amebelodon is another shovel-tusker from the Late Miocene of North America and China. At around 3 meters high, Platybelodon and Amebelodon were both similar in size to modern day elephants. The lower shovel-tusks may have been used to strip bark and vegetation from trees. Anancus was a gomphothere with only two tusks that looked much like a modern day elephant. However, its tusks were extremely long at 3 to 4 m. The fossil record of this organism ranges from the Late Miocene to the Pleistocene of Africa, Europe, and Asia. Anancus was adapted to a woodland life eating vegetation from trees and shrubs along with tubers growing in the ground. Stegomastodon from the Late Pliocene/Pleistocene of North and South America was one of the last gomphotheres to survive. Stegomastodon had two upward curing tusks and looked like a robust, compact version of a modern elephant. Stegomastodon migrated to South America during the Great American Interchange. Stegomastodon had cheek teeth covered in enamel and complex pattern of ridges. These teeth were suited for eating grass, indicating that this gomphothere had evolved into a grazer.

Stegodonts (family Stegodontidae) lived throughout Asia, Indonesia, and Japan during the Pliocene and Pleistocene. This family is closely related to living elephants. Some species of Stegodon looked like stocky version of a modern Asian Elephant. Species of Stegodon varied in size. Some were very large with a 4 m shoulder height and an 8 m long body (not including 3 m long tusks). Stegodon species that lived on islands often evolved into dwarf forms.

Mastodons (family Mammutidae) range from the Miocene to the Pleistocene. It is thought that mastodonts originated in Asia and spread to Africa, Europe, and North America (Benton, 2005, p. 327). Mammut americanum was a common proboscidean during the Miocene/Late Pleistocene of North America. Mammut americanum, like the mammoth, was covered in a shaggy coat of hair. Mammut was 3 m high at the shoulder and possessed two upward curving tusks. Heards of Mammut browsed in spruce woodlands up until about 10,000 years ago when they became extinct (Palmer, 2006, p. 386). Mammut americanum is the state fossil for Michigan.

Elephants and mammoths (family Elephantidae) radiated in the Late Miocene diversifying into many forms, today only three representatives survive. Mammoths were a diverse group of cold adapted elephant. Mammuthus columbi of the Late Pleistocene of North America was one of the largest species of elephant at 4 m high and 10,000 metric tons. During a Pleistocene ice age ocean levels dropped 300 feet thus connecting the Channel Islands to California. Twelve-foot tall Mammuthus columbi were free to migrate to the islands. As the climate warmed, the islands once again became isolated. The trapped mammoth population found no predators and fewer resources. Over thousands of years the giant skeletons were replaced by the pygmy Mammuthus exilis standing less than 2 m high and weighing less than 1 metric ton. Mammoths on the mainland remained large. Mammuthus columbi is the state fossil for Washington. The mammoth is the state fossil for Nebraska.

Mammuthus primigenius or the woolly mammoth of the Late Pleistocene was a cold climate tunda dweller. The woolly mammoth, at less than 3 m, was smaller than the modern elephant (typically 3.5 m at the shoulder). Woolly mammoths possessed an 8 cm thick layer of subcutaneous fat along with a shaggy coat of dark brown to black hair. A shoulder hump probably contained fat stores. Course hair up to 1 m in length covered the body with a woolly undercoat. Woolly mammoths had large curving tusks, up to 5 m long that were probably used to help scrape away ice and snow when grazing. Analysis of preserved Mammoth DNA indicates that mammoths were closely related to the modern African elephant (Benson, 2005, p. 328). Mammuthus primigenius survived up until about 10,000 years ago and are represented in cave paintings attributed to Cro-Magnon people. Fossil specimens with incredible soft tissue preservation have been found within the frozen tundra of Siberia and Alaska (see our section on fossil types). Populations of Mammuthus primigenius isolated on Wrangle Island and St. Paul Island evolved into dwarf varieties. Mammuthus primigenius is the state fossil for Alaska.

Literally hundreds of fossil elephant-like species have been described, but only three survive today, the Indian or Asia elephant (Elephas maximus), the African Bush Elephant (Loxodonta africana), and the African Forest Elephant (Loxodonta cyclotis). Elephants are the largest land animals extant today and are threatened by habitat destruction and poaching.

Xenarthra

Anteaters, Sloths & Armadillos

Anteaters, tree sloths, and armadillos represent modern edentates (superorder Xenarthra). The name edentate means without teeth, but this is true only for the anteater. Edentates evolved in isolation in South America during the Paleoence. Edentates migrated into North America via the Panamanian land bridge during the Pliocene. In the past this group was much more diverse and evolved into some truly amazing mammals. Megatherium, from the Pleistocene of South America, is the largest known ground sloth. Megatherium was a browsing herbivore that was the size of an elephant, but with a form reminiscent of a bear. This gigantic animal weighed in at over 3 tons and stood 6 meters tall when in a bipedal stance. Primarily a quadruped, Megatherium walked on the sides of its paws to accommodate its long claws. Glyptodon was a giant relative of the armadillo and is also found in the Pleistocene of South America. Glyptodon was a grazing herbivore that grew to over 2 m long and weighed in at 2 tons (Prothero, 2004, p. 404). Charles Darwin (1809-1882) became familiar with these fossils while serving as naturalist aboard the H.M.S. Beagle during the years of 1831 through 1836. Fossils such as Megatherium and Glyptodon were clearly related to but different from the organisms living in South America today. This biogeographical pattern through time was an important clue for Darwin that evolution had occurred.

Laurasiatheria

Laurasiatheria is a superorder that includes carnivores, even and odd-toed ungulates, pangolins, bats, shrews, moles and hedgehogs. Traditionally the origins of mammals have been placed among the insectivores probably because many early placental mammals have insectivorous teeth. The order Insectivora, which has been abandoned, included shrews, moles, hedgehogs, tenrecs, and golden moles. Tenrecs and golden moles have now been placed in Afrotheria. Shrews, hedgehogs, and moles are now grouped as Eulipotyphla.

Shrews, Moles, & Hedgehogs

The order Carnivora (Latin for flesh devour) includes cats, hyenas, dogs, weasels, civets, bears, seals, sea lions, and walruses. One should not confuse the word carnivore with the order Carnivora. Many members of the order Carnivora have adaptations for catching and eating prey such as meat tearing and shearing teeth, claws, and binocular vision. The word carnivore is used to identify an organism as a meat eater. Many members of the order Carnivora are carnivores, but other organisms that do not belong to this order can also be described as carnivores because of their diet, such as Killer Whales, theropod dinosaurs, and even insect digesting plants like the venus flytrap.

The order Carnivora can be divided into two suborders the Feliformia (cat-like forms) and the Caniformia (dog-like forms). Miacids (superfamily Miacoidea) represent basal carnivores. The fossil record of miacids ranges from the Paleocene to the Eocene. Miacids were small martin-like tree and ground dwelling carnivores. Modern groups diverged in the late Eocene and Oligocene.

Cats, Civets, Mongooses & Hyaenas

Feliforms include cats, civets, mongooses, hyaenas, and the extinct nimravids (Benton, 2005, p. 349). Nemravids (family Nimravidae) are the earliest group to evolve into cat-like forms. Although not true cats this family had a tendency to evolve into sabre-toothed forms. Barbourofelis of the late Miocene was a lion-sized saber-toothed nemravid. Proailurus (family Felidae) from the Oligocene and Miocene of Europe represents the first true cat. Proailurus was an ocelot-sized arboreal adapted animal with retractile claws. Felifoms radiated into many forms during the Miocene. Multiple genera of felids evolved into saber-toothed cats. Smilodon is probably the best-known sabre-toothed cat. Over 2000 skeltons of Smilodon have been found in the Pleistocene-aged Rancho La Brea tar pits in Los Angeles, California (Palmer, 2006, p. 368). Smilodon californicus is the state fossil for California. Hyenas (family Hyaenidae) are known from the Mid-Miocene.

Dogs, Weasels, Raccoons & Bears

Caniforms include dogs, arctoids, bears, raccoons, weasels and seals. Hesperocyon from the late Eocene to Oligocene of North America looks like a mongoose, but is revealed to be an early dog (family Canidae) by its ear and tooth structure. Weasels (family Mustelidae) are known from the Miocene and raccoons (family Procyonidae) are known from the Oligocene. Bears (family Ursidae) have a fossil record that dates back to the Eocene. Early bears, like Hemicyon, were dog-like in appearance. Bears have been very successful in the northern hemisphere. Perhaps the best-known fossil bear is the Ursus spelaeus (the cave bear). The cave bear lived in Europe during the Pleistocene and went extinct relatively recently only 27,000 years ago. The teeth of cave bears and isotope analysis of their bones suggest they were primarily herbivores. Cave bears were hunted and worshiped by Neanderthal people.

Seals, Sea Lions & Walrus

Current morphological and molecular data suggest that carnivores evolved into aquatic forms only once. Seals, sealions, and the walrus represent modern pinnipeds (Pinnipedia). The pinniped fossil record dates to the upper Oligocene. Puijila darwini from the early Miocene of Nunavut, Canada represents a transitional fossil that links terrestrial mammals to marine living seals. Puijila darwini superficially reminds one of an otter, but was actually an early semi-aquatic seal that adapted to a freshwater environment (Rybczynski, Dawson, & Tedford, p. 1023). Enaliarctos from the late Oligocene and early Miocene of California and Oregon is the most well represented early pinniped. Enaliarctos is thought to be an ancestor to modern pinniped groups. This 1.5 m long marine organism retained some primitive characteristics from its bear-like ancestor, such as a short tail and slicing carnassial teeth in contrast to modern pinnipeds piercing teeth designed for catching fish (Benton, 2005, p. 352). The limbs of Enaliarctos were modified into flippers, its eyes were large, and it possessed sensitive whiskers. By the Early to Middle Miocene members of the modern pinniped families, eared seals (Otariidae), walruses (Obodenidae), and true seals (Phocidae) appear in the fossil record (Kemp, 2005, p. 260).

Pangolins

Pangolins (order Philodota) or scaly anteaters are the only mammals with keratin scales covering their skin. When rolled up in a ball, these organisms resemble an artichoke. Extant or living scaly anteaters live in Africa and Southeast Asia. Pangolins have sharp claws and long sticky tongues, which make them well adapted for eating ants and termites. Eomanis from the Eocene of Germany may represent the earliest pangolin. Current molecular analysis places pangolins as a sister group to the order Carnivora (Benton, 2005, p. 353).

Artiodactyls

Even-toed ungulates (order Artiodactyla) include two major groups, the Suiformes (suborder Suina - pigs, peccaries, and hippopotamuses) and the Selenodontia (antelopes, camels, giraffes, cattle, and deer). Artiodactyls usually have 2 to 4 weight bearing toes (represented by the third and fourth toe) that form a semi-circular hoof. Another key feature of artiodactyls is their double pulley astragalus (an ankle bone) that allows bending between the lower leg and ankle while also restricting movement to the vertical plane. This signature characteristic makes their legs very efficient for front to back running motions.

Pigs, Peccaries & Hippopotamuses

The suborder Suina (pigs, peccaries, and hippopotamuses) groups the non-ruminant artiodactyls. Molars with large bulbous cusps and canine teeth with a triangular cross-section characterize Suiformes. Suiforme teeth represent adaptations for an omnivorous diet. Suiformes originated in Europe and Asia during the Middle Eocene and arrived in North America by the Late Eocene at which time they underwent an adaptive radiation. By the Late Oligocene suiformes arrived in Africa (Kemp, 2005, p. 264). During the Oligocene, North America was home to large pig-like animals known as entelodontids (family Entelodontidae). Entelodonts resembled pigs and had warthog-like bony protrusions on the sides of their skulls. Some reached hippo-size and existing on a diet of prey, carrion, and tubers. Daeodon (formerly Dinohyas) from the Miocene of North America represents the largest entelodont. Peccaries (family Tayassuidae) date from the Late Eocene of North America and Europe. True pigs (family Suidae) have a fossil record that dates bake to the Oligocene of Europe (Benton, 2005, p. 339). Anthracotheriids (family Anthracotheriidae) are an extinct family of hippo-like organisms that range from the Middle Eocene to the Late Pliocene of Europe, North America, and Africa. Anthracotheriids started out small, but reached small hippo-size. True hippos (family Hippopotamidae) date back to the Miocene. Today, only two species survive, Hippopotamus and the pigmy hippo Choeropsis, both are restricted to Africa (Benton, 2005, p. 340).

Antelopes, Camels, Giraffes, Cattle & Deer

Selenodonts (suborder Selenodontia: antelopes, camels, giraffes, cattle, and deer) have specialized square molars with crescent-shaped cusps on their teeth, two main toes (cloven hoofed), and a compound stomach, adapted for fermenting food (Benton, 2005, p. 340). Selenodonts can be further divided into two suborders, Tylopoda (camels, protoceratids, and oreodonts) and Ruminatia (cattle, sheep, antelope, giraffe, deer, and mouse deer).

Tylopods make their first appearance in the Late Eocene and diversified into many forms during the Oligocene and Miocene. Today only the camelids survive (family Camelidae: camels, llamas, alpacas, vicunas, and guanacos). Oreodonts were pig-sized animals that moved in herds through the woodlands and savannas of North America, browsing on low bushes. Oreodonts are common fossils in the Badlands of South Dakota. Protoceratids were deer-like artiodactyls that also grazed in herds. Many protoceratid males had bony outgrowths above their heads and snouts. Protoceratids flourished in North America from the Eocene to the Pliocene. Camels evolved in North America. Eocene forms were goat-sized animals with long necks and hooves on their two weight-bearing toes. The toes would eventually lose the hooves and fuse into a pad-like structure. Camels underwent an adaptive radiation during the late Oligocene and early Miocene. Camels diversified into many ecological niches with forms resembling deer, gazelles, and giraffes (Prothero, 2007, pp. 314-316). Camels reached North Africa and the Middle East by the late Miocene and Pliocene. Llamas reached South America during the Great American Interchange during the Pliocene 3 million years ago. Camels became extinct in North America by the end of the Pleistocene (Benton, 2005, p. 341). Although camelids are classified as a tylopod they do have something in common with the Ruminatia, they ruminate.

Ruminants

Camelids and Ruminatia ruminate to help extract the maximum nutritive value from their food. Camelids possess a three-chambered stomach, while Ruminatia (cattle, sheep, antelope, giraffe, deer, and mouse deer) possess a four –chambered stomach. Food is chewed and enters the first chamber where it is fermented. The food is now in the form of cud, which is regurgitated and chewed again. Chewing the cud is called ruminating. The cud is swallowed and is then digested as it passes through the entire alimentary canal. Camelids evolved the ruminant digestive process independently from other ruminants, thus it is an example of convergent evolution.

Ruminants started out as small hornless animals, but most groups evolved some kind of paired head ornaments. Horns are used to compete for females and to defend the herd and feeding territories. Modern ruminant groups representing the suborder Ruminatia (cattle, sheep, antelope, giraffe, deer, and mouse deer) radiated in the Miocene. Today only two giraffids (family Giraffidae) exist, the giraffe and the okapi. Giraffids diversified into many forms, most with short necks. Giraffes with long necks do not appear until the late Miocene. Giraffids have horn-like outgrowths, called ossicones, which are covered with skin. Many extinct forms had large branching ossicones reminiscent of moose and deer. Deer and moose (family Cervidae) have a fossil record that dates back to the Oligocene. The males of most deer species possess boney outgrowths called antlers (the only female deer with antlers are the Caribou). Antlers are shed and regrown annually. Each year new branches are acquired. Many extinct forms developed very large antlers. Today deer are the principal browsers in the Northern Hemisphere and in South America. The pronghorn antelope is the sole surviving species of a family (Antilocapridae), which is endemic to North America. Pronghorn antelope horns consist of a horny sheath that covers a boney core. The sheath is shed and regrown annually. Prognhorns were very diverse during the Miocene and Pliocene. Many species had multiple horns. Bovids (family Bovidae), which include true antelopes, cattle, bison, muskox, goats, sheep, water buffalo, and gazelles, have a fossil record that dates back to the early Miocene. Bovids have a bony horn core surrounded by a permanent sheath. Bovids originated in the Old World as small gazelle-like animals. Bovids underwent an adaptive radiation during the late Miocene as they adapted to open grassland habitats. Bovids migrated across the Bering land bridge to North America 1 million years ago, evolving into bison, bighorn sheep, and mountain goats (Palmer, 2006, p. 425). Africa is home to the largest number of modern bovids. The genus, Bos, to which modern cattle belong, dates back to the Pleistocene. Bos primigenius was domesticate some 6,000 years ago and is a subject of the 16,000-year-old cave paintings at Lascaux, in France (Palmer, 2006, p. 425).

Whales, Dolphins, & Porpoises

Molecular and fossil evidence clusters cetaceans (order Cetacea: whales, dolphins, and porpoises) within the even-toed ungulates artiodactyles (Kemp, 2005, p. 262). In fact, the closest living relative of the cetaceans is the hippopotamus. An amazing array of fossil discoveries, since the 1980’s, has helped to reveal the evolutionary transition of cetaceans from a terrestrial to a fully aquatic existence. We will mention just a few of the many transitional fossils now known. Pakicetus from the Early Eocene of Pakistan is a semi-aquatic coast-dwelling carnivore. Pakicetus was a dog-sized hoofed animal. Pakicetus had a double-pulley astragalus, the defining characteristic of an artiodactyle as well as an inner ear and tooth structure that help to reveal its tie to cetaceans. Ambulocetus (walking whale) from the Middle Eocene of Pakistan had flippers on both its forelimbs and hind limbs. The hind limbs still retained vestigial hooves. Ambulocetus was the size of a modern sea lion and its vertebrae suggest it swam with an up and down flexure of its body. Fully aquatic whales are known from the Middle to Late Eocene fossil record. Basilosaurus, from the Middle to Late Eocene deposits of Egypt, is fully aquatic. Basilosaurus was a 24 m long whale, but retained vestigial hind limbs, about the size of a human arm, embedded deep in the muscle tissue (Prothero, 2007). Basilosaurus cetoides is the state fossil for Alabama. Basilosaurus and Zygorhiza are the state fossils for Mississippi. After the Eocene whales radiated into two main groups, the toothed whales (Odontoceti) and the baleen whales (Mysticeti). Today, many modern whales possess the remnants of hip and thigh bones buried in muscles halfway down the body, revealing an evolutionary tie to their terrestrial ancestors (Prothero, 2007, p. 320). The fossil form of the beluga whale, Delphinapterus leucas, is the state fossil for Vermont.

Perissodactyles

Perissodactyles (Perissodactyla) include horses, tapirs, and rhinoceroses. Perissodactyles are the odd toed ungulates, having one, three or five toes. The odd-toed ungulates have a fossil record that dates back to the beginning of the Eocene in North America and Europe. Soon after their appearance they underwent an adaptive radiation, displacing basal placental groups (Benton, 2005, p. 346).

Horses

Horses represent some of the most primitive perissodactyles. Horses started out as dog-sized browsers that fed on the leaves of low vegetation. Fossil horses representing transitional forms show clear evolutionary trends related to adaptations acquired in response to changing environments. These evolutionary trends include a reduction in the number of toes, an increase in leg length and body size, as well as changes in tooth structure associated with changes in dietary habits. Hyracotherium had teeth adapted to browsing on leafy vegetation; it had four toes in the front and three on the back. Mesohippus had three toes and teeth adapted for browsing on the leaves of bushes and trees. Finally, Pliohippus had one toe and teeth adapted for grazing on grass. During the late Oligocene and early Miocene grasslands expanded in North America. The adaptations that horse lineages exhibit are associated with a reduction in forested areas as grasslands spread (Benton, 2005, p. 346). Longer legs with reduced number of toes made horses faster on the open grassland plains. Deep rooted, high crowned teeth provided horses with durable long lasting dentition needed to process grasses with high silica content, which is very abrasive. Equus simlicicidens is the state fossil for ldaho.

Tapirs

Tapirs were much more diverse during the Eocene. Early forms, such as Heptodon, of North America were rather horse-like. Over time tapirs evolved their distinctive short trunk or proboscis. Today tapirs are restricted to Central and South America, and Asia. Rhinoceroses in North America and Asia were very diverse during the Oligocene and Miocene, exhibiting a wide variety of body forms. Some were moderate in size similar to the horses and tapirs of the time, while others reached gigantic proportions. In fact, Paraceratherium (also known as Baluchitherium and Indricotherium) is the largest known land animal of all time at 5.4 m tall and weighing in at 15 metric tones. Horned rhinoceroses diversified during the Miocene. During the Eocene Perissodactyles dominated the woodlands of North America, but were displaced by Artiodactyles, especially ruminants, by the Mid-Miocene.

Brontotheres & Chalicotheres

The great perissodactyle adaptive radiation during the Eocene also resulted in two unusual ungulate families, the brontotheres (family Brontotheriidae or Titanotheriidae) and the chalicotheres (family Chalicotheriidae), which are now both extinct. The brontotheres started out as small hornless browsers, but evolved into large grazing animals that looked superficially like rhinoceroses. Many of these large forms had horns made of bony protuberances on their snout. Brontotheres grazed on soft vegetation and fruit. They died out at the end of the Eocene in North America, but persisted into the Oligocene in Asia (Benton, 2005, p. 349). Chalicotheres have a fossil range the spans from the Eocene to the Pleistocene. Chalicotheres started out as small forest animals but evolved into browsing animals with very long forelimbs and short hindlimbs. These evolutionary trends culminated in Chalicotherium of Africa and Europe. Chalicotherium had a horse-like head with a body that might remind one of a gorilla. Chalicotherium knuckle-walked and stood bipedally to pull branches down to access foliage (Benton, 2005, p. 348).

Bats

Bats (order Chiroptera) are the only mammals to evolve powered flight. Over 1,000 species of living bats are known with over 700 belonging to the suborder microchiroptera and over 200 belonging to the suborder megachiroptera. Microchiropterans are nocturnal insectivores that use echolocation to catch insects while in flight. Megachiropterans also known as fruit bats or flying foxes have an excellent sense of smell and subsist on fruit and nectar (frugivores). Most fruit bats do not use echolocation to navigate during flight. Bats are important plant pollinators’ worldwide. The forelimbs of bats are modified into wings formed from four elongated fingers connected with a thin membrane called the patagium. Bat remains are known from the Paleocene; however, the oldest well-known forms are Eocene. Eocene bats are already capable of flight, but do show some primitive characteristics. Onychonyceteris, from the Green River Formation of Wyoming, was a flying insectivore, but was not capable of using echolocation. Onychonyceteris means clawed bat and refers to the fact that, unlike modern forms, this form retained claws on all forelimb digits. The limb proportions of Onychonyceteris differ from modern forms, with the forelimbs shorter and the hindlimbs longer. Onychonyceteris was probably a good climber (Simmons, Seymour, Habersetzer, and Gunnell, 2008, pp. 818-822). Icaroycteris is known from the Green River Formation of Wyoming as well as the oil shale deposits of Messel in Germany. Icaronycteris was more like a modern insectivorous bat in that it could echolocate and had strong hindlimbs with the feet turned backwards so that it could hang upside down (Benton, 2005, p. 336). Icaronycteris also retained some primitive features. Icaronycteris retained claws on the thumb and first forefinger; modern forms have claw only on the shortened thumb for hanging. The tail of Icaronycteris was long and not connected to the hindlimbs with skin (Palmer, 2006, p. 355).

Euarchontoglires

Rodents

Euarchontoglires is a superorder that includes glires (rodents and lagomorphs) and euarchonta (primates, colugos, and tree shrews). Rodents (order Rodentia) make up the largest mammalian order today and with over 2,000 species accounts for 40% of all known mammals (Palmer, 2006, p. 426). Rodents are characterized by two deeply rooted, continuously growing upper and lower incisors. The incisors are sharpened and worn down by gnawing on wood, tough plant fibers, and nuts. Many rodents have a diet of seeds and plants. Basal rodents first appear in the Eocene and radiated into many forms in North America, Eurasia, and Africa. Rodents adapted to habitats occupied by multiberculates and may have been responsible for their decline in numbers. The oldest squirrels and beavers date back to the late Eocene. Palaeocastor is a well-known beaver form the Oligocene and Miocene of Nebraska. Palaeocastor made incredible vertical spiral burrows up to 2.5 m deep with an upper entrance and lower living chamber. These remarkable trace fossils are named Daimonelix (Benton, 2005, p. 356). The evolutionary line that leads to mice, rats, hamsters, and voles starts in the early Eocene. Eomys is an exceptionally preserved specimen from the Oligocene of Enspel, Germany. Specimens of Eomys are preserved with hair and skin. The skin preservation reveals that this organism was a glider. Mice and rats arose in the Eocene, but underwent a dramatic radiation in the Pleistocene. Rodents appear in the fossil record of Africa and South America in the early Oligocene. The South American lineage produced capybaras, guinea pigs, chinchillas, and new world porcupines. In South America, rodents diversified into some unusual forms and reached hippo-size (Kemp, 2005, p. 274). Phorusrhacos from the upper Miocene of Venezuela was 3 m long, stood 1.3 m tall at the shoulder, and weighed 700 kg (Benton, 2005, p. 358). Phorusrhacos was similar to the capybara and lived a semi-aquatic life. The capybara, at 50 kg, is the largest living rodent today.

Hares, Rabbits, & Pikas

Lagomorphs (order Lagomorpha) include hares, rabbits, and pikas. Lagomorphs have two pairs of incisors making a total of four. Like the rodents, lagomorphs must constantly chew to keep their continuously growing incisors at an optimum length.

Tree Shrews & Colugos

Euarchonta (primates, colugos, and tree shrews). Tree shrews are small, mostly arboreal, squirrel-like animals that inhabit tropical forests of Southeast Asia. The tree shrew has a poor fossil record; the earliest known fossil form is Eocene in age (Kemp, 2005, p. 273). The only surviving genus of the order Dermoptera is the flying lemur or colugo. Colugo’s live in the tropical forests of Southeast Asia and are adapted to an arboreal existence persisting on a herbivorous diet. They are the most capable of mammalian gliders. A wing-like skin the patagium connects the body, limbs and tail; even the toes are webbed. The parachute-like extension of the skin allows colugos to glide long distances from higher to lower tree locations. Fully developed dermopterans are known from the Eocene (Kemp, 2005, p. 272).

Primates

Primates (order Primates) include lemurs, lorises, tarsiers, monkeys, and apes. While many primates do not live in trees, they all possess adaptations for an arboreal way of life. In general, primates have binocular color vision, opposable thumbs, flattened nails instead of claws, generalist teeth, large brains compared to body size, one pair of mammary glands, reduced number of offspring with prolonged infant care, and complex social organizations. There are roughly 300 species of primates alive today and with the exception of humans they are restricted to mostly subtropical and tropical environments.

Plesiadapiformes

Plesiadapiformes are considered archaic primates and are sometimes classified as a suborder within Primates (Rose, 2006, p. 169). Plesiadapiformes were arboreal animals that ranged from shrew to marmot size. Their fossil record spans from the early Paleocene to the mid Eocene. Although found in Asia, they are particularly well represented in North America and Europe. Plesiadapis is perhaps the best-known plesiadapiform and was rather squirrel-like in their appearance, although they were beaver-size (Palmer, 2006, p. 430). Its long snout was equipped with large chisel-like teeth and grinding molars. The limb proportions and long tail of Plesiadapis reveal it was adapted for an arboreal existence. Its long fingers and toes ended in claws. A complete skeleton of Carpolestes has revealed these organisms possessed opposable, nail-bearing first digits. Some scientists believe these primate features may have evolved independently in this organism (Rose, 2006, p. 169).

Basal Primates

Omomyids and adapiforms are the oldest undisputed basal primates. Primates radiated in the Eocene and flourished in North America and Europe. Omomyids (family Omomyidae) were small tarsier-like organisms adapted for an arboreal life (Benton, 2005, p. 366). Omomyids had grasping hands and feet with fingers and toes that ended in nails. Their skeleton was designed as a tree dwelling quadruped capable of leaping from one branch to another (Rose, 2006, p. 188). Adapiforms (infraorder Adapiformes) are lemur-like primates that range from the early Eocene to the late Miocene. Adapiforms are found in Europe, North America, Africa, and Asia. Adapiforms are one of the most common primates in the fossil record. Their snouts were longer and their eye orbits smaller than omomyids. Some adapoids were adapted for grasping, climbing, and leaping, while others were adapted for actively running along branches (Rose, 2006, p. 180). The teeth of these early primates reveal that some were insectivores, while others were frugivores or leaf-eating herbivores.

Tarsiers

Tarsiers are the most ancient basal primates alive today. Tarsiers are known from the Eocene of Wyoming and China. Today tarsiers live in the islands of Southeast Asia. Tarsiers are small nocturnal arboreal animals that feed on insects and small animals. Tarsiers are agile climbers and jumpers. In fact, tarsiers are the best-adapted primates for leaping.

Lemurs & Lorises

Lemurs (infraorder Lemuriformes) and lorises (infraorder lorisiformes) are also extant basal primates. Today lemurs live in Madagascar and its surrounding islands. Lemurs are primarily arboreal animals that range from mouse to cat size. Lemurs have a toothcomb derived from the lower incisors and canines used for grooming and feeding. Although they have nails on their digits like all primates, they possess a toilet claw on the second toe. The locomotion of lemurs varies from climbing and leaping to quadrupedal running along branches. Some species are diurnal while others are nocturnal. Diets range from insects, fruit to small vertebrates. The lemur fossil record is poor and dates back to the Oligocene (Benton, 2005, p. 368). Lorisoforms include lorises and galagos (bush baby). Living lorises inhabit the central tropics of Africa and Southeast Asia. Lorises are small slender arboreal primates that are diurnal. There diet consists of insects, small vertebrates, and fruit. There motion of the lorises is often slow and deliberate, while the bush babies cling and leap. The loris fossil record dates back to the Eocene.

Monkeys & Apes

Anthropoids (suborder Anthropoidea) include the monkeys and apes. The anthropoid clade consists of two groups, one that evolved in the New World and one that evolved in the Old World. The New World monkeys are placed in the infraorder Platyrrhini. The Old World monkeys are placed in the infraorder Catarrhini. Both an African and Asian origin for anthropoids has been proposed based upon Eocene aged tooth and jaw fragments (Benton, 2005, p. 369).

New World Monkeys

Living platyrrhines are divided into two families, the Cebidae (capuchins, squirrel monkeys, tamarins, and marmosets) and the Atelidae (howlers and spider monkeys, saki, owl, and titi monkeys). The platyrrhine fossil record is poor and dates back to the Oligocene.

Catarrhines (infraorder Catarrhini) include the Old World monkeys (superfamily Cercopithecoidea) and the apes (superfamily Hominodea). The Eocene/Oligocene-aged Fayum deposits in Egypt produce some basal catarrhines, which predate the split between the Old World Monkeys and Apes. The most familiar of these fossil organisms is the Oligocene aged Aegyptopithecus. Aegyptopithecus is typical monkey-size and well adapted for an arboreal life style. Its teeth reveal it was most likely a frugivore (Kemp, 2006, p. 272).

The Old World monkeys can be divided into two groups, the cercopithecines (baboons, mandrills, macaques, and vervet monkeys) and the colobines (colobus monkeys, proboscis monkey, and langurs). The fossil record of Old World monkeys dates back to the lower Miocene of Africa, with modern genera not appearing until the Pliocene (Benton, 2005, p. 370). The oldest known fossil Old World monkey is Victoriapithecus found in early Miocene deposits near Lake Victoria in Africa (Kemp, 2005, p. 272).

Basal Apes

Living apes can be divided into the lesser apes (family Hylobatidae), which include gibbons and the siamang and the greater apes (family Hominidae), which include chimpanzees, gorillas, humans, and orangutans. Proconsul represents one of the first known fossil apes from the Lower Miocene of East Africa. Proconsul means “before consul”; the genus was named in 1933, apparently in reference to a performing chimpanzee named Consul at the London Zoo. Like many monkeys Proconsul lived a quadruped arboreal lifestyle, but like apes lacked a tail and possessed a relatively large brain. Proconsul had ape-like elbows and feet (Benton, 2005, p. 371). Proconsul represents a basal ape that lived before the divergence of the lesser and greater apes.

Gibbons

Gibbons are the most primitive of the living apes and have no known fossil representatives.

Living Hominidae can be divided into two subfamilies, the Ponginae (orangutans) and the Homininae (chimpanzees, gorillas, and humans). Kenyapithecus from the middle Miocene of Kenya is the oldest basal hominid known. This 1 m tall hominid climbed trees and lived on the ground. Sivapithecus from the middle to late Miocene is the oldest known ancestor to orangutans. Sivapithecus is known from Turkey, India, Pakistan, and China. Sivapithecus was probably much like the modern orangutan in diet and lifestyle. Dryopithecus is a small hominoid from the mid to upper Miocene of Europe, Spain, and Hungry. The forelimbs of Dryopithecus indicate that it was a climber or brachiator (using its arms to suspend and swing from branch to branch). Dryopithecus is usually placed between Proconsul and modern apes on cladograms (Benton, 2005, p. 375). The fossil record for chimpanzees and gorillas is practically non-existent at this point in time; however, this is not true for humans.

Several recent fossil finds add new evidence to early hominid evolution. Orrorin tugenensis is known from teeth, jaw fragments, and broken limb bones. Orrorin was excavated in Kenya from sediments dated as Miocene at 6 Ma. Evidence suggests that Orrorin may have been bipedal; however, interpretations of Orrorin remain controversial (Benton, 2005, p. 379. Sahelanthropus is known from a cranium and lower jaw fragments. The skull and teeth share characteristics with both chimpanzees and humans, making it a candidate for a basal hominid. Ardipithecus ramidus was found in Pliocene deposits in Ethiopia, dated at 4.4 Ma. Ardipithecus is known from skull fragments, teeth, and limb bones. Ardipithecus fossil remains provide evidence that it was a biped. Orrorin, Sahelanthropus, and Ardipithecus share primitive characteristics, but they also possess human-like characteristics, the most important of which is bipedalism; although, the case for bipedalism is not universally accepted for Orrorin and Sahelanthropus. Ardipithecus ramidus lived in a woodland environment and represents an intermediate form of hominid bipedalism (Gibbons, 2009, p. 36). A. ramidus could walk bipedally along the ground as well as walk comfortably along branches using its opposable thumbs and toes. The October 2, 2009 issue of Science has a special section dedicated to presenting 11 papers representing the work of an international, multidisciplinary team of scientists who have studied a site in Aramis, Ethiopia that has produced the fossil remains of at least 36 Ardipithecus individuals.

Australopithecines

The evolutionary line that leads to humans picks up again with the genus Australopithicus. The 3.2 Ma skeleton known as Lucy is the most complete skeleton representing Australopithicus afarensis. At 40% complete, Lucy’s skeleton reveals early hominin characteristics. Australopithicus afarensis was a little over 1 m tall and had a brain size of 415 cubic centimeters. Lucy retained some primitive characteristics such as a diastema (gap between the canine and incisors), longer arms and shorter legs, curved finger and toe bones for grasping limbs. However, Lucy’s femur, hip, along with the position of her skull above the spinal column provide evidence that she was fully adapted for bipedal locomotion. Australopithicus afarensis had lost the opposable toe retained by Ardipithecus. Like later species of Homo Au. afarensis had an inline toe adapted for more efficient bipedal locomotion. Sets of footprints preserved in a volcanic ash layer at Laetoli in Tanzania are believed to belong to Austrlopithicus afarensis. The footprints reveal two individuals walking upright side by side with a third, smaller, individual following. The footprints of other animals are also found in this volcanic ash layer. These important hominid trace fossils are dated at 3.6 Ma (Tattersal, Delson, & Van Couvering, pp. 212 & 213). Australopiths lived in Africa from the Miocene to the Pleistocene (3-1Ma) and diversified into many species representing multiple evolutionary lineages (Benton, 2005, p. 381). Some of the species include: anamensis, africanus, aethiopicus, robustus, and boisei.

Homo habilis

Homo habilis and Homo rudolfensis are the first fossils to be assigned to our genus. H. habilis and H. rudolfensis lived in Kenya Africa between 2.4 and 1.5 Ma. These hominids had brain sizes that ranged from 630 to 700 cubic centimeters. They stood at 1.3 m tall and possessed hands capable of fine manipulation. H. habilis is associated with the Oldowan stone tool industry, which spans from 1.9 to 1.6 Ma. Oldowan tools are pieces of stone modified by stone-on-stone chipping (Tattersal, Delson, & Van Couvering, 1999, pp. 387-390). These tools are worked on only one side of the stone. Oldowan choppers and scrappers are associated with animal bones that exhibit cut marks.

Homo erectus

Homo erectus fossils range from 1.9 to 0.5 Ma, making it the longest lived member of our family. Early H. erectus specimens have a brain size of between 800 and 900 cubic centimeters. We should note that some paleontologists use Homo ergaster to classify H. erectus remains found in Africa. H. erectus migrated from Africa to Europe and Asia. Thus, H. erectus was the first member of our family to leave Africa. H. erectus fossils from China dated at 0.2 Ma have brain sizes that had increased to between 900 and 1100 cubic centimeters (Benton, 2005, p. 383). The post cranial skeleton of H. erectus is much like modern Homo sapiens and falls within the lower end of modern heights (Tattersal, Delson, & Van Couvering, 1988, pp 263 & 264). H. erectus is associated with more complex tools than H. habilis and possibly the use of fire (Benton, 2005, p. 383). H. erectus is associated with the Acheulean tool industry, which spans from 1.5 to 0.2 Ma in Africa, Europe, and Asia. These tools are characterized by chipping on two sides of the stone (bifacially flaked). Handaxes, cleavers, and picks are common Acheulean tools. These tools are later associated with some groups of Homo sapiens (Tattersal, Delson, & Van Couvering, 1988, pp 3-5). Oldawan and Acheulean tools are classified as Old Stone Age or early Paleolithic. Several named species may actually be examples of H. erectus including: antecessor, cepranensis, ergaster, georgicus, mauritanicus, and soloensis (Lahr and Foley, 2004, p. 1044). Homo antecessor is known from a juvenile specimen from Spain. This fossil dates to 0.78 Ma. Tools associated with this specimen are pre-Acheulean. Some scientists argue that H. antecessor represents a common ancestor for Neanderthals and modern H. sapiens; however, this is somewhat controversial since the species is defined using a juvenile specimen.

Homo heidelbergensis

Homo heidelbergensis fossils range from 0.8 to 0.4 Ma. H. heidelbergensis is more advanced than H. erectus, but ancestral to Neanderthals. H. heidelbergensis had a cranial capacity that averaged 1200 cubic centimeters. H. heidelbergensis lived during the middle Pleistocene in Europe and Africa and is associated with Acheulean tools. H. heidelbergensis were making throwing spears up to 3.2 m long 400,000 years ago in Germany. The spears are associated with butchered horses, deer, rhino, bear, and elephants (Cowen, 2005, p. 289).

Homo floresiensis

Recently, the fossils of a pygmy-sized hominin were found in a cave on the island of Flores in Indonesia. Homo floresiensis stood 1 m tall and had a brain capacity of 380 cubic centimeters. H. floresiensis is associated with bifaically worked stone tools and the remains of dwarfed Stegodon. The deposit is Late Pleistocene and dated at around 18,000 years old. In reference to evidence gathered at the site the authors suggest that H. floresiensis was preferentially hunting juvenile dwarf Stegodon (Morwood, 2004, p. 1089). H. floresiensis is believed to be a dwarfed descendant of H. erectus based upon some shared derived skeletal features (Brown, 2004, p. 1061). Island dwarfism is well known among mammals, but H. floresiensis is the first hominin example of this phenomenon (Lahr & Foley, 2004, p. 1044). H. floresiensis is an interesting evolutionary side branch.

Homo neaderthalensis

Neanderthal (Homo neanderthalensis) fossils range from 400,000 to 30,000 years ago. Neanderthal brain size averages 1450 cc, which is larger than modern humans that average 1360 cc (Benton, 2005, pp. 384 & 385). The neanderthal body is somewhat shorter and more heavily built than modern humans. This body type indicates that Neanderthals were adapted for cold weather (Tattersal, Delson, & Couvering, 1988, p. 370). Neanderthal people have been found in Europe, Asia, and the Middle East, but are most abundant in central Europe. Neanderthals were hunters and gathers. Like modern humans they took care of injured individuals and buried their dead (Tattersal, Delson, & Couvering, 1988, p. 370). Neanderthal people are associated with the Mousterian stone-tool industry, which dates from possibly 150,000 years to 35,000 years ago (they are also associated with Acheulean tools at some sites. Mousterian tools include flaked stone hand axes, scrappers, backed knives, and leaf-shaped points. The Mousterian stone-tool industry is also associated with some archaic-modern humans. Mousterian tools are classified as Middle Paleolithic (Tattersal, Delson, & Couvering, 1988, p 360). Neanderthals diverged from modern humans 0.5 Ma (Benton, 2005, p. 385).

Homo sapiens

Modern humans (Homo sapiens) range from 160,000 years ago to the present (Benton, 2005, p. 385). The Cro-Magnon people of Europe (40,000-30,000 years ago) are associated with Upper Paleolithic tools, carved art objects, and the cave paintings of France. Archaic H. sapiens increasingly used bone, ivory, and wood to make more sophisticated tools. Benton (2005, p 387) recognizes major benchmarks in human evolution:

Scientists and philosophers debate whether or not evolution is progressive. Is there a trend in efficiency, complexity, and intelligence? This article mentions only a small fraction of the known fossil mammals within major clades. When examined in detail the fossil record of each group, even humans, exhibits an evolutionary pattern that is very bushy. The branch that ends with humans is only one of thousands of mammalian evolutionary lines; however, it is special in that it represents a way for the universe to known itself. Modern humans are the first organisms to comprehend and appreciate the history of life on Earth.

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