TRACING THE HUMAN EVOLUTION- PRIMATES TO RACES..

M. JAGATHEESWARII M.Sc. SPECIAL ZOOLOGYUNIVERSITY OF MADRAS

OBJECTIVE

Tracing and understanding the human origin and evolution,with reference to fossil and genetic evidences.

PRIMATE EVOLUTIONEUARCHONTA Euarchonta are the grand order of mammals

containing the orders of extinct Pleisiadapiformes, Scadentia or tree shrews and Primates.

Arose around 88mya. However earliest fossils recorded is around 65mya (Purgatorious coracis).

Small ,nocturnal, arboreal, insect eating mammals Includes Primates and Stem primates.

Purgatorious coracis

STEM PRIMATES- Pleisiadapis Includes Pleisiadapis from the order

Pleisiadapiformes. Considered to be the ancestor of all

the primates. Lived about 55mya. First to develop finger nails, and

front facing eyes. Dentition showed functional shift

towards omnivority. Placed as a sister group to Primates.

PRIMATES

First or most completely developed members of the animal world. ( J.Z. Young)

Primate = Prime, first rank (Latin) Characterized by large brains compared to

mammals, increased reliance towards steroscopic vision at the expense of olfactory senses.

Includes the suborders : Strepsirrhini Haplorrhini

STREPSIRRHINI

Includes Prosomians,Lemurs, and Lorises.

Characterised by their wet nose or Rhinarium

Rhinarium is connected to the upper lip

HAPLORRHINI

Defined by their dry nose where rhinarium is replaced by more mobile and continuous upper lip.

Includes Tarsiers , Simian monkeys, and Apes.

Further dived into suborders

Platyrrhini Catarrhini

PLATYRRHINI

Includes new world monkeys.

Examples: Spider monkeys, howler monkeys.

Characteristics includes Prehensile tail, Flat nose (with nostrils flaring out), adaptation for arborel life with long limbs, delicate hands and tails for balancing and seizing.

CATARRHINI Includes Cercopithecoidea –

the old world monkeys. Larger than new world

monkeys. Characteristics includes small

tail, naked, highly coloured rear which becomes enlarged in females before ovulation.

Eg: Rhesus monkey (Macaque), Sacred Baboon (Papio), Mandrill( Mandrillus).

PROCONSUL

Split from Cercopithecoidea about 20mya.

Best known african genus is Proconsul africanus.

Branched off before the split of greater and lesser apes.

Had both Cercopithecoidea and Ape characterstics.

Proconsul africanus

CERCOPITHECOIDEA APE

Thin toothed enamel Light build and

Narrow chest Short forelimbs Arboreal

Quadrupedal lifestyle.

No tail Ape like elbows Larger brain than the

body size

HOMINIDAE

Includes greater apes like Pongo (Orangutans), Pan (Chimpanzee), Gorilla (Gorrila), and lesser apes like Hylobates (Gibbons)

DIVERGENCE OF HUMANS FROM OTHER APES

Hylobates (Gibbons)• First to diverge • About 15 mya.

Pongo ( Orangutans)• About 13 mya

Gorrila (Gorrila)• Speciated from Pan and human lineage.• About 10 mya

Pan ( chimpanzees)Speciated from human lineage About 7 mya

EARLIEST HOMININSSahenlanthropus tchadensis

Last common ancestor for human and chimpanzees

Lived about 7-6 mya. Discovered in 2001, near

Chad,Western Africa. had both ape like and human

like characteristics.

Sahenlanthropus tchadensis

APE HUMAN Small brain Sloping face Very prominent

brow ridges Elongated skull

Small canine teeth Short middle part of

the face. Spinal cord opening

underneath the skull instead of the back.

Orrorin tugenesis Lived about 6.2 – 5.8 mya. Discovered in Kenya. Position of Foramen magnum suggests

bipedalism. Post cranium suggests they climbed

trees. Had smaller teeth than the

Australopithecines. Some consider it as the human ancestor

rather than the Australopithecines. If proven then Australopithecines will be

the side branch of the human family tree.

Sahenlanthropus Orrorin tchadensis tugenesis

Ardipithecus kadabba Lived about 5.8-5.2 mya in

eastern Africa. Discovered in 1997,Kenya. Bipedal, canine resembled later

hominins Toe has robust appearance

suggesting bipedal push off. Diet included fibrous foods.

Ardipithecus ramidus Lived about 4.4 mya in Eastern Africa. Discovered in 1994. Pelvis- both arboreal and bipedal . Brain was small ( 300-350cc) Feet – adaptation for grasping more

than walking. Pelvis, angle of Foramen magnum,

thin wrists suggests Bipedalism. Diet – omnivorous, non preference to

hard nuts and tubers.

AUSTRALOPITHECINES-Australopithecus afarensis

Lived about 3.8-2.9mya in eastern Africa.

Discovered in 1974. Nicknamed ‘Lucy’.

Foot prints of a couple in volcanic ash ( Lateoli foot prints) – Bipedalism.

Had both ape and human characteristics.

Australopithecus afarensis

APE HUMAN Flat nose. Protruding jaw Small brain Curved fingers

Small canine and molars Bipedal gait Lower vertebrae modified

to support to bipedalism even during pregnancy.

MISSING LINK?? In 2015, jaw bone had been

found in Ethiopia. Argued to be earliest Homo

(2.8mya) that links Austraopithecines to Homo.

Bipedal, enlarged brain, hands suitable for tool making.

Not assigned to specific species yet.

EARLY HOMOHomo habilis

Lived in Eastern Africa about 2.3mya.

Earliest member of the genus Homo

Larger brain, smaller face, teeth than Australopithecines

Ape like long arms and moderately prognathic face.

First to make tools – ‘Handy man’.

Chief predator of habilis and Australopithecines – Dinofelis

Led to the development of stone making abilities and living in group for protection.

PARANTHROPUS Includes P. robustus, P. aethiopicus,

P. boisei Lived about 2.3- 1.2 mya in Eastern

Africa. Branched off from H.habilis. Strong Jaw for eating nuts- thus

named ‘nut cracker man’. Extinct due to lack of diet adaptations Side branch of human lineage- did

not lead to human evolution.

Homo erectus (1.8 mya) Lived in Africa and Asia. Homo

who lived the longest. Large brain, smaller teeth, less

sloping forehead, elongated legs and, shorter arms than torso.

Completely erect gait. First to migrate outside Africa. Used fire. Height 4.9-6feet weight 40-68kgs.

Homo ergaster Homo pekinensis Lived about 1.5 mya Evolution of dark skin

happened during its time indicating that the loss of body hair is complete.

Nick named ‘peking man’.

Lived in Asia. Considered not to be

the direct ancestors of humans but cousins that emerged from H.erectus

Homo antecessor Lived about 1.2 mya Considered to be the

common ancestor for humans and Neanderthals.

Cut marks on the skulls and bones discovered suggests that they practiced cannibalism.

LATER HOMOHomo heidelbergensis Lived about 700k-200k years

ago in eastern and southern Africa, Europe and Asia.

Discovered in 1908. Large brow ridge, larger

braincase, flatter face than early Homo.

First to hunt large animals, create simple dwellings

( Terra amata,France). Larger and more muscular than

modern humans.

Homo neanderthalensis (400k-40kya)

Discovered in 1829. Our closest extinct human

relative. Shorter , stockier, had large

brain and body. Used Tools,clothes, painted

on caves,lived in groups, buried the dead.

Diet was omnivorous.

Extinction- causes not known-perhaps lack of better adaptation or pathogen infection from migrated H.sapiens might have caused the extinction.

No violent interactions with H.sapiens found (infact they coexisted and inter bred).

H.neanderthals disappeared all of a sudden despite having bigger brain capacity (1400cc) and burlier body , and the H.sapiens (1300cc and gracile ) survived.

Perhaps it is the Survival of the weakest in our case.

Homo sapien idaltu (160kya) Extinct sub species of Homo sapiens

sapiens. Discovered in 1997, Ethiopia. Globular braincase and face like

humans,though huge and robust. Fossils-Non neanderthal. Shows modern humans evolved in

Africa long before neanderthals in Europe.

Thus there is no Neanderthal stage in human evolution.

DENISOVANS (30k- 50kya) Discovered in 2010 in Denisova

cave, Siberia Cave also had Neanderthal

fossils(dated 45kya) and human fossils.

Gene sequencing- non neanderthal Also some of the DNA in

Australian aborigines is from them.

Indicates interbreeding b/w archaic H.sapiens, H.neanderthals and denisovans

Homo floresiensis (18kya) Until recently it was thought that we were

the only hominin existed after the neanderthal extinction about 40kya.

But H.floresiensis was discovered in 2003 from Flores, Indonesia, which is supposed to have lived along with Homo sapiens

Showed Rapid reduction in body size. Considered as human hobbit. But argued that the cranium used to

describe the species could have been example of Microcephaly.

Still unresolved.

Homo sapien sapien(200kya) Only living Homo. Originated from eastern africa and spread to all

corners of the world. Also caleed Cro-magnon man or Omo. Characterised by Skull- thin walled & high vaulted to

accommodate large brain. Distinct chin. Near vertical fore head. Much less(if any) eyebrow ridges. Much less prognathism. Jaws with small teeth. Lighter build. Large brain capacity-1300cc.

HYPOTHESIS FOR HUMAN ORIGINS

MULTI REGIONAL ORIGIN

RECENT AFRICAN ORIGIN

MULTI -REGIONAL ORIGIN Proposed by Milford Wolpoff in 1984. Modern humans arose about 2mya and

subsequent human evolution has been within a single species.

This species encompasses all archaic humans such as the H.erectus, H.neanderthal as well as the modern forms and evolved world wide to diverse population of Homo sapien sapiens.

Genes exchanged between continental populations via cross migration enabling various groups to reach the same Homo sapien sapien status.

Major blow- Mitochondrial eve , Y chromosomal adam, anatomically modern human fossils( idaltu).

THE RECENT AFRICAN ORIGIN(OUT OF AFRICA)

Homo sapiens evolved from Homo erectus only in Africa.

Migrated from Africa about 100kya. Widely accepted. Genetic evidence(mt eve, Y chromosomal

adam) and fossil evidence(idatu) suggests anatomically modern humans evolved solely in Africa b/w 200k-60kya.

H.sapiens left africa and replaced other homos such as H.neanderthal and H. erectus.

Also archaic humans may have interbred with other homo to give rise to modern humans

MITOCHONDRIAL EVE (140k-200kya)

Alan Wilson et al proposed it in 1979. Published on ‘nature’ in 1987.

Matrilineal most recent common ancestor(MRCA) of all the currently living humans.

We descend in an unbroken line , on our mother’s side & mothers of our mothers and so on untill all lines converge on one woman.

mtDNA is passed from mother without recombination.

Lived after H.heidelbergiensis and after the emergence of H. neanderthal in Africa.

Boost to ‘out of Africa’ hypothesis.

Y-CHROMOSOMAL ADAM

Patrilineal most recent common ancestor.

Male who was the last one from whom all males inherit their Y chromosome.

A phylogenetic analysis of more than 1500 individuals from all continents traced the Y chromosome to a common African ancestor.

Confirms ‘out of Africa’ hypothesis.

EVOLUTION OF RACES All contemporary humans are members of the same

polytypic specie, Homo sapien sapiens. People are clumped together in a particular race by

characteristics such as the skin colour, face shape,hair colour and form, skin around the eyes, eye colour etc.

CAUSES: Global cooling trend, about 1,30,000 years ago caused average drop in temperature.

Homo sapiens moved to different regions and were isolated long enough and inherited some traits.

Darkness of the skin decreased with increasing latitude. Major races of today are

Caucasians,Blacks,Mongoloids, and Australoids

CAUCASIANS : White skinned people majorly seen in europe. They have orthognathic face with vertically straight fore head.Have 4% Neanderthal genes.

BLACKS: Negroes include the native African and Afro-americans. They have prognathic face, bigger teeth, lips, concave forehead).

MONGOLOIDS: Yellow skinned people of the Asian continent with characteristic facial features ( flat face, epicanthic folds)

AUSTRALOIDS: Includes the native Australians ( Australian aborigines) and the Dravidians( Tamils) of south India.

It is believed that the Australoids and negroes have the most primitive features( proganthic face, concave forehead).

RECENT EVOLUTION OF MAN It’s a most common misconception that the humans

had stopped evolving. But The Natural selection still affects the humans. Current evolution seen in man are Delay of the menopause and early puberty in females

resulting in the lengthening of the reproductive period. Reduction in blood glucose levels, cholesterol levels

and blood pressure in some populations.(Human diet is high in fats and calories, there is currently a selective pressure going on to make the humans more adapted to these diets and thus more resistant to diseases.)

Lactase persistence ( lactose intolerance has been greatly reduced).

Loss of wisdom tooth owing to the smaller jaw( about 35% of the population today does not develop wisdom tooth, as evolution tends to favour the elimination of the unwanted traits to save the unnecessary energy expenditure it takes to develop it).

Blending of races- due to globalization there are very few populations that remains isolated. Thus the racial differences are gradually disappearing.

Decrease in robust muscular strength ( studies show we’re weaker than our ancestors).

Loss of Palmaris longus in 10% of the world population.

CONCLUSION Homo sapiens are the apex beings of our

world today. But on seeing the grand scheme, we’re the

youngest beings on earth. Our existence of about 200k years is nothing

compared to the other organisms or even our hominin ancestors who lived longer than us.

Adaptation, natural selection,and genetical evolution shaped our species to what we’re today and is still shaping us toward our future.

REFERENCES FOR FURTHER READINGBIBLIOGRAPHY•Concepts of biology – Sylvia S.Mader•Evolution- Nicholas H.Barton et al•Evolution(4th edition ) – Strickberger•Evolutionary Analysis(4th edition)- Scott freeman & Jon C.Herron•Human and primate evolution- Susan cachel•Human evolution- Birdsell•Human genetics- Russ Hodge•Humankind emerging (9th edition) - Bernard G.Campbell et al•Introduction to physical Anthropology(2009-2010 edition)- Robert Jurmain et al•Neanderthals and modern humans-Clive Finlayson•Primates of the world- Rod & Ken preston•Principles of organic evolution-E.k .Iyer•Smithsonian intimate guide to human origin- Carl Zimmer•The Descent of man- Charles Darwin•The life of Vertebrates- J.Z.Young•The Rise of Homo sapiens- Fredrick L. Coolidge & Thomas wynn•What on the Earth evolved – Christopher llyod

Websites and e-journals•Bradshawfoundation.com•Forbes.com – missing link fossil found (2015)•Humanorigins.si.edu•Leakeyfoundation.org•Mhrc.net – Mitochondrial Eve•Mnn.com – Projecting Human Evolution( 2012)•Modern humans came out of Africa-Owen James, National geographic news(2007)•Nature.com•Sciencemag.org – molecular genomic data identify the closest living relative of primates , Jan E. Janeka et al•Scientificamerican.com•Usnews.com (2012)

-Descent of man,1871

THANK YOU COUSINS !!!