Timeline of human evolution

Haeckel's Paleontological Tree of Vertebrates (c. 1879).
The evolutionary history of species has been described as a "tree", with many branches arising from a single trunk. While Haeckel's tree is somewhat outdated, it illustrates clearly the principles that more complex modern reconstructions can obscure.

The timeline of human evolution outlines the major events in the development of the human species, and the evolution of humans' ancestors. It includes a brief explanation of some animals, species or genera, which are possible ancestors of Homo.

It does not address the origin of life, which is addressed by abiogenesis, but presents one possible line of descendants that led to humans. This timeline is based on studies from paleontology, developmental biology, morphology and from anatomical and genetic data. The study of human evolution is a major component of anthropology.

Homo sapiens taxonomy

The cladistic line of descent (taxonomic rank) of Homo sapiens (modern humans) is as follows:

Taxonomic rankNameCommon nameMillions of
years ago
DomainEukaryotaCells with a nucleus2,100
KingdomAnimaliaAnimals590
PhylumChordataVertebrates and closely related invertebrates530
SubphylumVertebrataVertebrates505
SuperclassTetrapodaTetrapods395
UnrankedAmniotaAmniotes, tetrapods that are fully terrestrially-adapted340
ClassMammaliaMammals220
SubclassTheriiformesMammals that birth live young (i.e. non-egg-laying)
InfraclassEutheriaPlacental mammals (i.e. non-marsupials)125
MagnorderBoreoeutheriaSupraprimates, bats, whales, most hoofed mammals, and most carnivorous mammals
SuperorderEuarchontogliresSupraprimates (primates, rodents, rabbits, tree shrews, and colugos)100
GrandorderEuarchontaPrimates, colugos and tree shrews
MirorderPrimatomorphaPrimates and colugos79.6
OrderPrimatesPrimates75
SuborderHaplorrhini"Dry-nosed" (literally, "simple-nosed") primates (apes, monkeys, and tarsiers)40
InfraorderSimiiformes"Higher" primates (or Simians) (apes, old-world monkeys, and new-world monkeys)
ParvorderCatarrhini"Downward-nosed" primates (apes and old-world monkeys)30
SuperfamilyHominoideaApes28
FamilyHominidaeGreat apes (Humans, chimpanzees, gorillas, and orangutans)15
SubfamilyHomininaeHumans, chimpanzees, and gorillas8
TribeHomininiGenera Homo and Australopithecus, sometimes Pan is also included5.8
SubtribeHominina Contains only the Genus Homo2.5
GenusHomoHumans2.5
Species(Archaic) Homo sapiensModern humans0.5
SubspeciesHomo sapiens sapiensFully anatomically modern humans0.2

Timeline

First living beings

Date Event
4000 Ma
(million
years ago)		 The earliest life appears.
Further information: Abiogenesis
3900 Ma Cells resembling prokaryotes appear. This marks the first appearance of photosynthesis and therefore the first occurrence of large quantities of oxygen on the earth.
Further information: Cell (biology) § Evolution
2500 Ma First organisms to utilize oxygen. By 2400 Ma, in what is referred to as the Great Oxygenation Event, the pre-oxygen anaerobic forms of life were wiped out by the oxygen consumers.
2100 Ma More complex cells appear: the eukaryotes.
1200 Ma Sexual reproduction evolves, leading to faster evolution.[1]
900 Ma
Choanoflagellate

The choanoflagellates may look similar to the ancestors of the entire animal kingdom, and in particular they may be the direct ancestors of Sponges.[2][3] Proterospongia (members of the Choanoflagellata) are the best living examples of what the ancestor of all animals may have looked like.

They live in colonies, and show a primitive level of cellular specialization for different tasks.

600 Ma It is thought that the earliest multicellular animal was a sponge-like creature.

Sponges are among the simplest of animals, with partially differentiated tissues.

Sponges (Porifera) are the phylogenetically oldest animal phylum extant today.

580 Ma Multicellular animal movement may have started with cnidarians. Almost all cnidarians possess nerves and muscles. Because they are the simplest animals to possess them, their direct ancestors were very probably the first animals to use nerves and muscles together. Cnidarians are also the first animals with an actual body of definite form and shape. They have radial symmetry. The first eyes evolved at this time.
550 Ma
Flatworm
Flatworms are the earliest animals to have a brain, and the simplest animals alive to have bilateral symmetry. They are also the simplest animals with organs that form from three germ layers.
540 Ma Acorn worms are considered more highly specialised and advanced than other similarly shaped worm-like creatures. They have a circulatory system with a heart that also functions as a kidney. Acorn worms have a gill-like structure used for breathing, a structure similar to that of primitive fish. Acorn worms are thus sometimes said to be a link between vertebrates and invertebrates.

Chordates

Date Event
530 Ma
Pikaia
Pikaia is an iconic ancestor of modern chordates and vertebrates.[4] Other, earlier chordate predecessors include Myllokunmingia fengjiaoa,[5] Haikouella lanceolata,[6] and Haikouichthys ercaicunensis.[7]

The lancelet, still living today, retains some characteristics of the primitive chordates. It resembles Pikaia.

Conodont

Conodonts are a famous type of early (495 Mya and later) chordate fossil; they are the peculiar teeth of an eel-shaped animal characterized by large eyes, fins with fin rays, chevron-shaped muscles and a notochord. The animal is sometimes called a conodont, and sometimes a conodontophore (conodont-bearer) to avoid confusion.

505 Ma
Agnatha

The first vertebrates appear: the ostracoderms, jawless fish related to present-day lampreys and hagfishes. Haikouichthys and Myllokunmingia are examples of these jawless fish, or Agnatha. (See also prehistoric fish). They were jawless and their internal skeletons were cartilaginous. They lacked the paired (pectoral and pelvic) fins of more advanced fish. They were precursors to the Osteichthyes (bony fish).[8]

480 Ma
A Placoderm

The Placodermi were prehistoric fishes. Placoderms were some of the first jawed fishes (Gnathostomata), their jaws evolving from the first gill arch.[9] A placoderm's head and thorax were covered by articulated armoured plates and the rest of the body was scaled or naked. However, the fossil record indicates that they left no descendents after the end of the Devonian and are less closely related to living bony fishes than sharks are.

410 Ma The first coelacanth appears;[10] this order of animals had been thought to have no extant members until living specimens were discovered in 1938. It is often referred to as a living fossil.

Tetrapods

Date Event
390 Ma
Panderichthys

Some fresh water lobe-finned fish (Sarcopterygii) develop legs and give rise to the Tetrapoda.

The first tetrapods evolved in shallow and swampy freshwater habitats.

Primitive tetrapods developed from a lobe-finned fish (an "osteolepid Sarcopterygian"), with a two-lobed brain in a flattened skull, a wide mouth and a short snout, whose upward-facing eyes show that it was a bottom-dweller, and which had already developed adaptations of fins with fleshy bases and bones. The "living fossil" coelacanth is a related lobe-finned fish without these shallow-water adaptations. These fishes used their fins as paddles in shallow-water habitats choked with plants and detritus. The universal tetrapod characteristics of front limbs that bend backward at the elbow and hind limbs that bend forward at the knee can plausibly be traced to early tetrapods living in shallow water.[11]

Panderichthys is a 90–130 cm (35–50 in) long fish from the Late Devonian period (380 Mya). It has a large tetrapod-like head. Panderichthys exhibits features transitional between lobe-finned fishes and early tetrapods.

Trackway impressions made by something that resembles Ichthyostega's limbs were formed 390 Ma in Polish marine tidal sediments. This suggests tetrapod evolution is older than the dated fossils of Panderichthys through to Ichthyostega.

Lungfishes retain some characteristics of the early Tetrapoda. One example is the Queensland Lungfish.

375 Ma
Tiktaalik

Tiktaalik is a genus of sarcopterygian (lobe-finned) fishes from the late Devonian with many tetrapod-like features. It shows a clear link between Panderichthys and Acanthostega.

365 Ma
Acanthostega
Ichthyostega

Acanthostega is an extinct amphibian, among the first animals to have recognizable limbs. It is a candidate for being one of the first vertebrates to be capable of coming onto land. It lacked wrists, and was generally poorly adapted for life on land. The limbs could not support the animal's weight. Acanthostega had both lungs and gills, also indicating it was a link between lobe-finned fish and terrestrial vertebrates.

Ichthyostega is an early tetrapod. Being one of the first animals with legs, arms, and finger bones, Ichthyostega is seen as a hybrid between a fish and an amphibian. Ichthyostega had legs but its limbs probably weren't used for walking. They may have spent very brief periods out of water and would have used their legs to paw their way through the mud.[12]

Amphibia were the first four-legged animals to develop lungs which may have evolved from Hynerpeton 360 Mya.

Amphibians living today still retain many characteristics of the early tetrapods.

300 Ma
Hylonomus

From amphibians came the first reptiles: Hylonomus is the earliest known reptile. It was 20 cm (8 in) long (including the tail) and probably would have looked rather similar to modern lizards. It had small sharp teeth and probably ate millipedes and early insects. It is a precursor of later Amniotes and mammal-like reptiles. Αlpha keratin first evolves here which is used in claws in modern lizards and birds, and hair in mammals.[13]

Evolution of the amniotic egg gives rise to the Amniota, reptiles that can reproduce on land and lay eggs on dry land. They did not need to return to water for reproduction. This adaptation gave them the capability to colonize the uplands for the first time.

Reptiles have advanced nervous systems, compared to amphibians. They have twelve pairs of cranial nerves.

Mammals

Date Event
256 Ma
Phthinosuchus, an early Therapsid
Shortly after the appearance of the first reptiles, two branches split off. One branch is the Sauropsids, from which come the modern reptiles and birds. The other branch is Synapsida, from which come modern mammals. Both had temporal fenestrae, a pair of holes in their skulls behind the eyes, which were used to increase the space for jaw muscles. Synapsids had one opening on each side, while diapsids had two.

The earliest mammal-like reptiles are the pelycosaurs. The pelycosaurs were the first animals to have temporal fenestrae. Pelycosaurs are not therapsids but soon they gave rise to them. The Therapsida were the direct ancestor of mammals.

The therapsids have temporal fenestrae larger and more mammal-like than pelycosaurs, their teeth show more serial differentiation, and later forms had evolved a secondary palate. A secondary palate enables the animal to eat and breathe at the same time and is a sign of a more active, perhaps warm-blooded, way of life.[14]

220 Ma
Cynognathus

One sub-group of therapsids, the cynodonts, evolved more mammal-like characteristics.

The jaws of cynodonts resemble modern mammal jaws. It is very likely that this group of animals contains a species which is the direct ancestor of all modern mammals.[15]

220 Ma
Repenomamus

From Eucynodontia (cynodonts) came the first mammals. Most early mammals were small shrew-like animals that fed on insects. Although there is no evidence in the fossil record, it is likely that these animals had a constant body temperature and milk glands for their young. The neocortex region of the brain first evolved in mammals and thus is unique to them.

Monotremes are an egg-laying group of mammals represented amongst modern animals by the platypus and Echidna. Recent genome sequencing of the platypus indicates that its sex genes are closer to those of birds than to those of the therian (live birthing) mammals. Comparing this to other mammals, it can be inferred that the first mammals to gain gender differentiation through the existence or lack of SRY gene (found in the y-Chromosome) evolved after the monotreme lineage split off.

160 Ma
Juramaia sinensis

Juramaia sinensis[16] is the earliest known eutherian mammal fossil.

100 Ma Last common ancestor of mice and humans (base of the clade Euarchontoglires).

Primates

Date Event
85–65 Ma
Plesiadapis
Carpolestes simpsoni

A group of small, nocturnal and arboreal, insect-eating mammals called the Euarchonta begins a speciation that will lead to the primate, treeshrew and flying lemur orders. The Primatomorpha is a subdivision of Euarchonta that includes the primates and the stem-primates Plesiadapiformes. One of the early stem-primates is Plesiadapis. Plesiadapis still had claws and the eyes located on each side of the head. Because of this they were faster on the ground than on the top of the trees, but they began to spend long times on lower branches of trees, feeding on fruits and leaves. The Plesiadapiformes very likely contain the species which is the ancestor of all primates.[17]

One of the last Plesiadapiformes is Carpolestes simpsoni. It had grasping digits but no forward-facing eyes.

63 Ma Primates diverge into suborders Strepsirrhini (wet-nosed primates) and Haplorrhini (dry-nosed primates). Strepsirrhini contain most of the prosimians; modern examples include the lemurs and lorises. The haplorrhines include the three living groups: prosimian tarsiers, simian monkeys, and apes. One of the earliest haplorrhines is Teilhardina asiatica, a mouse-sized, diurnal creature with small eyes. The Haplorrhini metabolism lost the ability to make its own Vitamin C. This means that it and all its descendants had to include fruit in its diet, where Vitamin C could be obtained externally.
30 Ma
Aegyptopithecus

Haplorrhini splits into infraorders Platyrrhini and Catarrhini. Platyrrhines, New World monkeys, have prehensile tails and males are color blind. They may have migrated to South America on a raft of vegetation across the relatively narrow Atlantic ocean (approx. 700 km). Catarrhines mostly stayed in Africa as the two continents drifted apart. Possible early ancestors of catarrhines include Aegyptopithecus and Saadanius.

25 Ma
Proconsul

Catarrhini splits into 2 superfamilies, Old World monkeys (Cercopithecoidea) and apes (Hominoidea). Our trichromatic color vision had its genetic origins in this period.

Proconsul was an early genus of catarrhine primates. They had a mixture of Old World monkey and ape characteristics. Proconsul's monkey-like features include thin tooth enamel, a light build with a narrow chest and short forelimbs, and an arboreal quadrupedal lifestyle. Its ape-like features are its lack of a tail, ape-like elbows, and a slightly larger brain relative to body size.

Proconsul africanus is a possible ancestor of both great and lesser apes, including humans.

Hominidae

Date Event
15 Ma Hominidae (great apes) speciate from the ancestors of the gibbon (lesser apes).
13 Ma Homininae ancestors speciate from the ancestors of the orangutan.[18]

Pierolapithecus catalaunicus is believed to be a common ancestor of humans and the great apes or at least a species that brings us closer to a common ancestor than any previous fossil discovery. It had special adaptations for tree climbing, just as humans and other great apes do: a wide, flat rib cage, a stiff lower spine, flexible wrists, and shoulder blades that lie along its back.

10 Ma The lineage currently represented by humans and the Pan genus (common chimpanzees and bonobos) speciates from the ancestors of the gorillas.
7 Ma
Sahelanthropus tchadensis

Hominina speciate from the ancestors of the chimpanzees. Both chimpanzees and humans have a larynx that repositions during the first two years of life to a spot between the pharynx and the lungs, indicating that the common ancestors have this feature, a precondition for vocalized speech in humans. The latest common ancestor lived around the time of Sahelanthropus tchadensis, ca. 7 Ma ; S. tchadensis is sometimes claimed to be the last common ancestor of humans and chimpanzees, but there is no way to establish this with any certainty. The earliest known representative from the ancestral human line post-dating the separation with the chimpanzee lines is Orrorin tugenensis (Millennium Man, Kenya; ca. 6 Ma).

4.4 Ma Ardipithecus is a very early hominin genus (tribe Hominini or subtribe Hominina). Two species are described in the literature: A. ramidus, which lived about 4.4 million years ago[19] during the early Pliocene, and A. kadabba, dated to approximately 5.6 million years ago[20] (late Miocene). A. ramidus had a small brain, measuring between 300 and 350 cm3. This is about the same size as modern bonobo and female common chimpanzee brain, but much smaller than the brain of australopithecines like Lucy (~400 to 550 cm3) and slightly over a fifth the size of the modern Homo sapiens brain. Ardipithecus was arboreal, meaning it lived largely in the forest where it competed with other forest animals for food, including the contemporary ancestor for the chimpanzees. Ardipithecus was probably bipedal as evidenced by its bowl shaped pelvis, the angle of its foramen magnum and its thinner wrist bones, though its feet were still adapted for grasping rather than walking for long distances.
3.6 Ma
Australopithecus afarensis
Some Australopithecus afarensis left human-like footprints on volcanic ash in Laetoli, Kenya (Northern Tanzania) which provides strong evidence of full-time bipedalism. Australopithecus afarensis lived between 3.9 and 2.9 million years ago. It is thought that A. afarensis was ancestral to both the genus Australopithecus and the genus Homo. Compared to the modern and extinct great apes, A. afarensis has reduced canines and molars, although they are still relatively larger than in modern humans. A. afarensis also has a relatively small brain size (~380–430 cm³) and a prognathic (i.e. projecting anteriorly) face. Australopithecines have been found in savannah environments and probably increased its diet to include meat from scavenging opportunities. An analysis of Australopithecus africanus lower vertebrae suggests that females had changes to support bipedalism even while pregnant.
3.5 Ma Kenyanthropus platyops, a possible ancestor of Homo, emerges from the Australopithecus genus.
3 Ma The bipedal australopithecines (a genus of the Hominina subtribe) evolve in the savannas of Africa being hunted by Dinofelis. Loss of body hair takes place in the period 3-2 Ma, in parallel with the development of full bipedalism.

Homo

Date Event
2.8 Ma
Homo habilis

Appearance of Homo. Homo habilis is thought to be the ancestor of the lankier and more sophisticated Homo ergaster. Lived side by side with Homo erectus until at least 1.44 Ma First stone tools, beginning of the Lower Paleolithic.

Further information: Homo rudolfensis
1.8 Ma
A reconstruction of Homo erectus.

Homo erectus evolves in Africa. Homo erectus would bear a striking resemblance to modern humans, but had a brain about 74 percent of the size of modern man. Its forehead is less sloping than that of Homo habilis and the teeth are smaller. Other hominid designations such as Homo georgicus, Homo ergaster, Homo pekinensis, Homo heidelbergensis are often put under the umbrella species name of Homo erectus.[21] Starting with Homo georgicus found in what is now the Republic of Georgia dated at 1.8 Ma, the pelvis and backbone grew more human-like and gave H. georgicus the ability to cover very long distances in order to follow herds of other animals. This is the oldest fossil of a hominid found outside of Africa. Control of fire by early humans is achieved 1.5 Ma by Homo ergaster. Homo ergaster reaches a height of around 1.9 metres (6.2 ft). Evolution of dark skin, which is linked to the loss of body hair in human ancestors, is complete by 1.2 Ma. Homo pekinensis first appears in Asia around 700 Ka but according to the theory of a recent African origin of modern humans, they could not be human ancestors, but rather, were just a cousin offshoot species from Homo ergaster. Homo heidelbergensis was a very large hominid that had a more advanced complement of cutting tools and may have hunted big game such as horses.

1.2 Ma Homo antecessor may be a common ancestor of humans and Neanderthals.[22][23] At present estimate, humans have approximately 20,000–25,000 genes and share 99% of their DNA with the now extinct Neanderthal [24] and 95-99% of their DNA with their closest living evolutionary relative, the chimpanzees.[25][26] The human variant of the FOXP2 gene (linked to the control of speech) has been found to be identical in Neanderthals.[27] It can therefore be deduced that Homo antecessor would also have had the human FOXP2 gene.
600 ka
A reconstruction of Homo heidelbergensis

Three 1.5 m (5 ft) tall Homo heidelbergensis left footprints in powdery volcanic ash solidified in Italy. Homo heidelbergensis may be a common ancestor of humans and Neanderthals.[28] It is morphologically very similar to Homo erectus but Homo heidelbergensis had a larger brain-case, about 93% the size of that of Homo sapiens. The holotype of the species was tall, 1.8 m (6 ft) and more muscular than modern humans. Beginning of the Middle Paleolithic.

200 ka Omo1, Omo2 (Ethiopia, Omo river) are the earliest fossil evidence for anatomically modern Homo sapiens.[29]

The hypothetical man Y-chromosomal Adam is estimated to have lived in Africa 254 (95%-CI 192–307) kya ago by a 2015 study.[30] He is the most recent common ancestor from whom all male human Y chromosomes are descended.

160 ka Homo sapiens (Homo sapiens idaltu) in Ethiopia, Awash River, Herto village, practice mortuary rituals and butcher hippos. Potential earliest evidence of anatomical and behavioral modernity consistent with the continuity hypothesis including use of red ochre and fishing.[31]

The hypothetical woman Mitochondrial Eve is estimated to have lived in East Africa between 99 000 and 200 000 years ago, the most recent female ancestor common to all mitochondrial lineages in humans alive today. Note that there is no evidence of any characteristic or genetic drift that significantly differentiated her from the contemporary social group she lived with at the time. Her ancestors were Homo sapiens as were her contemporaries.

90 ka Appearance of mitochondrial haplogroup L2.
70 ka Behavioral modernity according to the "great leap forward" theory.[32]
60 ka Appearance of mitochondrial haplogroups M and N, which participate in the migration out of Africa. Homo sapiens that leave Africa in this wave start interbreeding with the Neanderthals they encounter.[33][34]
50 ka Migration to South Asia. M168 mutation (carried by all non-African males). Beginning of the Upper Paleolithic. mt-haplogroups U, K.
40 ka Migration to Australia[35] and Europe (Cro-Magnon).
25 ka The independent Neanderthal lineage dies out. Y-Haplogroup R2; mt-haplogroups J, X.
10-20 ka Beginning of the Mesolithic / Holocene. Y-Haplogroup R1a; mt-haplogroups V, T. Evolution of light skin in Europeans (SLC24A5).[36][37] Homo floresiensis dies out, leaving Homo sapiens as the only living species of the genus Homo.

See also

General:

References

  1. ↑ "'Experiments with sex have been very hard to conduct,' Goddard said. 'In an experiment, one needs to hold all else constant, apart from the aspect of interest. This means that no higher organisms can be used, since they have to have sex to reproduce and therefore provide no asexual control.'
    Goddard and colleagues instead turned to a single-celled organism, yeast, to test the idea that sex allows populations to adapt to new conditions more rapidly than asexual populations." Sex Speeds Up Evolution, Study Finds (URL accessed on January 9, 2005)
  2. ↑ Dawkins, R. (2005), The Ancestor's Tale: A Pilgrimage to the Dawn of Evolution, Houghton Mifflin Harcourt, ISBN 978-0-618-61916-0
  3. ↑ "Proterospongia is a rare freshwater protist, a colonial member of the Choanoflagellata." "Proterospongia itself is not the ancestor of sponges. However, it serves as a useful model for what the ancestor of sponges and other metazoans may have been like." http://www.ucmp.berkeley.edu/protista/proterospongia.html Berkeley University
  4. ↑ "Obviously vertebrates must have had ancestors living in the Cambrian, but they were assumed to be invertebrate forerunners of the true vertebrates — protochordates. Pikaia has been heavily promoted as the oldest fossil protochordate." Richard Dawkins 2004 The Ancestor's Tale Page 289, ISBN 0-618-00583-8
  5. ↑ Shu, D. G.; Luo, H. L.; Conway Morris, S.; Zhang, X. L.; Hu, S. X.; Chen, L.; Han, J.; Zhu, M.; Li, Y.; Chen, L. Z. (1999). "Lower Cambrian vertebrates from south China". Nature 402 (6757): 42. Bibcode:1999Natur.402...42S. doi:10.1038/46965.
  6. ↑ Chen, J. Y.; Huang, D. Y.; Li, C. W. (1999). "An early Cambrian craniate-like chordate". Nature 402 (6761): 518. Bibcode:1999Natur.402..518C. doi:10.1038/990080.
  7. ↑ Shu, D. G.; Morris, S. C.; Han, J.; Zhang, Z. F.; Yasui, K.; Janvier, P.; Chen, L.; Zhang, X. L.; Liu, J. N.; Li, Y.; Liu, H. -Q. (2003), "Head and backbone of the Early Cambrian vertebrate Haikouichthys", Nature 421 (6922): 526–529, Bibcode:2003Natur.421..526S, doi:10.1038/nature01264, PMID 12556891
  8. ↑ These first vertebrates lacked jaws, like the living hagfish and lampreys. Jawed vertebrates appeared 100 million years later, in the Silurian. http://www.ucmp.berkeley.edu/vertebrates/vertintro.html Berkeley University
  9. ↑ "Bones of first gill arch became upper and lower jaws." (Image)
  10. ↑ A fossil coelacanth jaw found in a stratum datable 410 mya that was collected near Buchan in Victoria, Australia's East Gippsland, currently holds the record for oldest coelacanth; it was given the name Eoactinistia foreyi when it was published in September 2006.
  11. ↑ "Lungfish are believed to be the closest living relatives of the tetrapods, and share a number of important characteristics with them. Among these characters are tooth enamel, separation of pulmonary blood flow from body blood flow, arrangement of the skull bones, and the presence of four similarly sized limbs with the same position and structure as the four tetrapod legs." http://www.ucmp.berkeley.edu/vertebrates/sarco/dipnoi.html Berkeley University
  12. ↑ "the ancestor that amphibians share with reptiles and ourselves? " " These possibly transitional fossils have been much studied, among them Acanthostega, which seems to have been wholly aquatic, and Ichthyostega" Richard Dawkins 2004 The Ancestor's Tale page 250, ISBN 0-618-00583-8
  13. ↑ Eckhart L, Valle LD, Jaeger K; Valle; Jaeger; Ballaun; Szabo; Nardi; Buchberger; Hermann; Alibardi; Tschachler et al. (November 2008). "Identification of reptilian genes encoding hair keratin-like proteins suggests a new scenario for the evolutionary origin of hair". Proceedings of the National Academy of Sciences of the United States of America 105 (47): 18419–23. Bibcode:2008PNAS..10518419E. doi:10.1073/pnas.0805154105. PMC 2587626. PMID 19001262.
  14. ↑ "In many respects, the pelycosaurs are intermediate between the reptiles and mammals" http://www.ucmp.berkeley.edu/synapsids/pelycosaurs.html Berkeley University
  15. ↑ "Thrinaxodon, like any fossil, should be thought of as a cousin of our ancestor, not the ancestor itself. It was a member of a group of mammal-like reptiles called the cynodonts. The cynodonts were so mammal-like, it is tempting to call them mammals. But who cares what we call them? They are almost perfect intermediates." Richard Dawkins 2004 The Ancestor's Tale page 211, ISBN 0-618-00583-8
  16. ↑ A Jurassic eutherian mammal and divergence of marsupials and placentals http://dx.doi.org/10.1038/nature10291
  17. ↑ "Fossils that might help us reconstruct what Concestor 8 was like include the large group called plesiadapi-forms. They lived about the right time, and they have many of the qualities you would expect of the grand ancestor of all the primates" Richard Dawkins 2004 The Ancestor's Tale page 136, ISBN 0-618-00583-8
  18. ↑ Raauma, Ryan, Sternera, K., (2005) "Catarrhine primate divergence dates estimated from complete mitochondrial genomes", Journal of Human Evolution 48: 237-257
  19. ↑ Perlman, David (July 12, 2001). "Fossils From Ethiopia May Be Earliest Human Ancestor". National Geographic News. Retrieved July 2009. Another co-author is Tim D. White, a paleoanthropologist at UC-Berkeley who in 1994 discovered a pre-human fossil, named Ardipithecus ramidus, that was then the oldest known, at 4.4 million years.
  20. ↑ White, Tim D.; Asfaw, Berhane; Beyene, Yonas; Haile-Selassie, Yohannes; Lovejoy, C. Owen; Suwa, Gen; WoldeGabriel, Giday (2009). "Ardipithecus ramidus and the Paleobiology of Early Hominids.". Science 326 (5949): 75–86. Bibcode:2009Sci...326...75W. doi:10.1126/science.1175802. PMID 19810190.
  21. ↑ NOVA: Becoming Human Part 2 http://video.pbs.org/video/1319997127/
  22. ↑ J. M. Bermúdez de Castro, et al. A Hominid from the Lower Pleistocene of Atapuerca, Spain: Possible Ancestor to Neandertals and Modern Humans. Science 1997 May 30; 276: 1392-1395.
  23. ↑ Green, R. E., Krause, J, Ptak, S. E., Briggs, A. W., Ronan, M. T., Simons, J. F., et al. (2006) Analysis of one million base pairs of Neanderthal DNA. Nature, 16, 330–336. http://www.nature.com/nature/journal/v444/n7117/abs/nature05336.html
  24. ↑ "Rubin also said analysis so far suggests human and Neanderthal DNA are some 99.5 percent to nearly 99.9 percent identical." Neanderthal bone gives DNA clues (URL accessed on November 16, 2006)
  25. ↑ "The conclusion is the old saw that we share 98.5% of our DNA sequence with chimpanzee is probably in error. For this sample, a better estimate would be that 95% of the base pairs are exactly shared between chimpanzee and human DNA." Britten, R.J. (2002). "Divergence between samples of chimpanzee and human DNA sequences is 5%, counting indels". PNAS 99 (21): 13633–5. Bibcode:2002PNAS...9913633B. doi:10.1073/pnas.172510699. PMC 129726. PMID 12368483.
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