Phylogeny from genetics and themaking of Homo sapiens-1

Bipedalism

Bipedalism Foramen Magnum

Knee Comparisons

3 - 4 mya

Foot Comparisons

Phylogeny from genetics and themaking of Homo sapiens-1

Dental Changes

?

Dental differences

• By comparison to apes, humans have:– smaller canines

• no gap between upper canine and premolar

• no honing first lower premolar

– relatively small central incisors

– relatively large molars

– very thick molar enamel

– a parabolic rather than U-shaped dentalarch

Sahelanthropus tchadensisSahelanthropus tchadensis

Sahelanthropus tchadensisSahelanthropus tchadensis

• Toros-Menalla locality, Djurab Desert, northern Chad• Fauna includes aquatic and amphibious animals

alongside gallery forest and savanna fauna– Fish, crocodiles, primates, rodents, elephants, equids,

bovids– Suggests hominid lived close to a lake, but not far from a

sandy desert

• Age between 6 and 6½ million years• Unique mosaic of primitive and derived characters

– Primitive (ape-like)• very small cranial capacity (320-380 cc)• large central incisor• non-incisiform canines

– Derived (human like)• Very slightly reduced canines• thick molar enamel• nuchal crest positioning suggesting bipedalism

Sahelanthropus tchadensisSahelanthropus tchadensis

SahelanthropusAustralopithecus

Homo sapiens Chimp

Are these lines off becauseof deformation of the fossil?

Orrorin tugenensis

• Dated at 6 m.y.a.

• Primitive:

– Anterior teeth are small and chimp-like

– Humerus for climbing

• Hominid-like:

– Thick molar enamel

– Femur shows aspects of bipedalismOrrorinOrrorin

tugenensistugenensis

Ardipithecus ramidus kadabbaArdipithecus ramidus kadabbaToe boneToe bone

MandibleMandiblefragmentfragment

Published by AAAS

B. Hanson Science 326, 60-a-61-a (2009)

Ardipithecus ramidusArdipithecus ramidus

Lovejoy’s reconstruction Cladogram of Ardi

Phylogeny from genetics and themaking of Homo sapiens

Lots of different ways of doing hominid inour early days

Phylogeny from genetics and themaking of Homo sapiens

Early adaptive radiation, between4 and 2½ mya. Same time as split

in chimpanzee lineage.

AustralopithecusAustralopithecus anamensisanamensis

• ~4 mya

• Teeth– Thick molar enamel

– Relatively large canines

– Sectorial lower firstpremolar

• Post-crania– Femur indeterminate

– Both ends of tibiaconsistent with bipedality

– Arm bones hominid-like,but useful for tree-climbing

Australopithecus anamensis

Australopithecus afarensisAustralopithecus afarensisLucy: 40% complete skeletonLucy: 40% complete skeleton

Australopithecus afarensisfootprints

• Laetoli

• Discovered by MaryLeakey

• Volcanic tuff dated atalmost 3.5 millionyears

• Upright, bipedallocomotion of two orthree hominids

Kenyanthropus platyopsKenyanthropus platyops

Holotype KNM-WT 40000 a, left lateral view (markers indicate the plane separating the distorted neurocranium andthe well-preserved face). b, Superior view. c, Anterior view. d, Occlusal view of palate. Paratype KNM-WT 38350. e,Lateral view. KNM-WT 40001. f, Lateral view. g, Inferior view. Scale bars: a–c, 3 cm; d–g, 1 cm. (Leakey et al. 2001)

Phylogeny from genetics and themaking of Homo sapiens

•Later adaptive radiation 2¼ to ~1¾mya

•Many mammalian species radiatingat the Pliocene- Pleistoceneboundary as the Earth cools andenters the “Ice Age”

Two Different Lineages

• Hominids split during this period ofextreme climatic change with tougherplant foods into two lineages:

1. A group of very large jawed heavychewers (Paranthropus)

2. A group that retains slighter jaws butshow cranial expansion (Homo)

TaungTaung Child: discussed by Wells, p. 36Child: discussed by Wells, p. 36

Mrs. (?)Mrs. (?) PlesPles (Sts 5)(Sts 5)

AustralopithecusAustralopithecus africanusafricanus

AustralopithecusAustralopithecusgarhigarhi

Photograph by David Brill

Australopithecus (Paranthropus)Australopithecus (Paranthropus) aethiopicusaethiopicus

Photograph by Robert I.M. Campbell

AustralopithecusAustralopithecus (Paranthropus)(Paranthropus) robustusrobustus

OH 7OH 7

Photograph by John Reader

Homo habilisHomo habilis

Discovery of thisjaw in 1960 ledLouis Leakey toname a new species,Homo habilis, asdirect ancestor ofman, with Homoerectus representingan extinct sidebranch

KNMKNM--ER 1813ER 1813

Photograph by John Reader

Photograph by David Brill

HomoHomohabilishabilis

Homo rudolfensisHomo rudolfensisKNMKNM--ER 1470ER 1470

Photographs by David Brill

Phylogeny from genetics and themaking of Homo sapiens-1

Long LegsBig Brains

Big Jaws

AustralopithecusAustralopithecus(Paranthropus)(Paranthropus)boiseiboiseiKNMKNM--ER 406ER 406

Photograph by David Brill

PhylogenyHomo ergasterHomo ergaster

~ 1.8~ 1.8--1.6 mya1.6 myaFirst to leave AfricaFirst to leave Africa

Homo erectusHomo erectusZhoukoudianZhoukoudian OriginalOriginal PithecanthropusPithecanthropus

erectuserectus fossils discoveredfossils discoveredby Dubois in museum caseby Dubois in museum case

Homo erectusHomo erectus

• Wolpoff claims that H. erectus is an invalidtaxon, though few accept this interpretation atthis point in time

• Others believe the material attributed toerectus should be split into several differenttaxons– Asian and later African material remaining as H.

erectus--not contributing to modern humans

– Early African material as H. ergaster

– European material as H. heidelbergensis

Homo erectus

• An increase in brain size to approximately900 cc

• Reduction in postcanine dentition and adecrease in jaw size

• Vertical shortening of the face.• Shortening arm bones, especially forearms to

very modern limb proportions– Postcranial proportions are very similar to

tropically adapted modern humans

• Development of a more barrel-shaped chest• The formation of an external nose• Modern human size in terms of height

Plio-Pleistocene Setting

• There is little average change in temperaturebetween 2.5 mya and today– Dramatic changes in amplitude of changes

– Breakpoint about 600,000 years ago• The Ice Ages with periods of extensive glaciation in high

latitudes alternating with brief warm periods

• The beginning of extreme fluctuationcoincides with advanced Homo erectus(Homo heidelbergensis)– Continuing fluctuation produces Archaic Homo

sapiens

Plio-Pleistocene Climates

Less Ice

More Ice

FirstPleistocenetransition

Phylogeny

First Pleistoceneclimate transition

Mid-Pleistocene ClimateTransition The pattern of

fluctuationschanges

dramatically

starting around

900 kya

Thousands of years ago

Phylogeny

Second Pleistoceneclimate transition

Homo antecessorHomo antecessorGranGran DolinaDolina, Spain, Spain

~750~750 –– 900 kya900 kya

Photograph by Javier Trueba

Homo antecessor

• Securely dated at 780 kyr• Approximate brain size of 1000 cc• Marked double-arched browridge

– like later Neanderthals and Chinese H. erectus

• Canine fossa but no expanded maxilla– May be due to the individual's young age since others (ATD 6-58) have

an expanded maxilla

• Sharp nasal margin• Shallow maxillary notch• Reduced mandibular corpus thickness when compared to H.

ergaster or early H. erectus• Small postcanines that resemble those of the habilines• M3 reduced relative to M1• Moderate taurodontism

– Characteristic of H. erectus and H. heidelbergensis)

• Large I2 dimensions that resemble H. heidelbergensis

Homo antecessor• An important feature that was discovered when the

remains were examined were cut marks that werepresent on most of the material– 12 parallel cut marks on a temporal fragment where the

sternocleidomastoid muscle attaches– Cut marks on two foot phalanges where the flexor muscle

lies

• Dismemberment was the likely goal• Faunal material shows the same cut marks as the

hominid remains– Very few carnivore tooth marks indicates that hominids

were mainly responsible for processing the bones

• This is the earliest well-documented case ofcannibalism in a hominid population, and thisinformation is important for deciphering the behaviorof early hominids

Photographs by David Brill

Homo heidelbergensisHomo heidelbergensisfrom Arago, Francefrom Arago, France

~300~300 –– 400 kya400 kya

Homo heidlebergensis

• An increase in brain size to approximately1200cc

• A shift in the widest part of the brain casefrom the cranial base to the parietal regions

• The rear of the cranial vault becomes morevertical

• A gradual reduction in cranial robusticity• A decline in postcranial robusticity• A tendency for a shift from shorter more

robust stature to taller, leaner bodies

MauerMauer 11HomoHomo heidlebergensisheidlebergensis

Photograph by John Reader Germany, Age est. 500 kya (400Germany, Age est. 500 kya (400 –– 700 kya)700 kya)

Mid to late PleistoceneMid to late Pleistocene HomoHomo

Arago: 400 kyaBodo: 600 kya

heidelbergensis erectus