The Drastic change…….

Name- Lalit KumarClass-XSec-ARoll No.-18

Darwin and Human EvolutionLamarck posed the

hypothesis about our relation to apes before Darwin

Darwin published “Descent of Man” in 1871

Caused criticism of his theory, but already the basic ides of evolution had taken hold in the scientific community.

Human Evolution IntroHuman evolution is the lengthy process of change by which people

originated from apelike ancestors. Scientific evidence shows that the physical and behavioral traits shared by all people originated from apelike ancestors and evolved over a period of approximately six million years.

One of the earliest defining human traits, bipedalism -- the ability to walk on two legs -- evolved over 4 million years ago. Other important human characteristics -- such as a large and complex brain, the ability to make and use tools, and the capacity for language -- developed more recently. Many advanced traits -- including complex symbolic expression, art, and elaborate cultural diversity -- emerged mainly during the past 100,000 years.

Humans are primates. Physical and genetic similarities show that the modern human species, Homo sapiens, has a very close relationship to another group of primate species, the apes. Humans and the great apes (large apes) of Africa -- chimpanzees (including bonobos, or so-called “pygmy chimpanzees”) and gorillas -- share a common ancestor that lived between 8 and 6 million years ago.

Primates•A primate is a mammal of the order Primates.• In taxonomy, primates include two distinct lineages, strepsirrhines and haplorhines.•Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment. Most primate species remain at least partly arborcal.

Origins estimated back to 65 Million Years Ago . Oldest fossil only goes back 45 Million Years Ago . Insect eating nocturnal mammal. Derived traits for life in trees in the tropics. Grasping hands and feet. Separate big toe / thumb. Sensitive Skin ridges on hands and feet. Large brains – eye hand coordination- brachiating. Short jaws. Forward looking eyes – close together, stereo vision. Flat nails – not claws. Long parental care with learned behaviors. Single births. Fully opposable thumb.

What’s new in Primates

Primate groupsPROSIMIANS

Include Lemurs, Tarsiers.Probably more similar to origin arboreal

ancestral primatesANTHROPOIDS

Include Monkeys, Apes and Humans.Split from the Prosimians about 45 Million

Years Ago

Anthropoids Include the Monkeys and the HominoidsMonkeys evolved in two areas ,split about

35 million years ago New World monkeys (older),

all arboreal have prehensile tail, nostrils open to the sides Squirrel and capuchin monkeys

Old World monkeys both arboreal and ground dwellers Lack prehensile tail, nostrils open downwards Rhesus monkey, baboons, macaques

Hominoids Include Great Apes and Humans

Apes: Gibbons, Orangutan, Gorillas, Chimpanzee/ Bonobo Split from monkeys about 20-25MYALarger brain size to body size ratios than other primatesMore flexible behavior (less instinct, more learned behaviors)Mostly larger than monkeys (except gibbons) Have long arms, short legs and no tail.Gibbons and orangutans primarily arborealGorillas, Chimps and Humans

Social behaviorPrimarily terrestrial Chimps more closely related to humans than gorillas.

Hominoids(apes)

Kingdom- Animalia Phylum- Chordata Clade- Synapsida Class- Mammalia Order- Primates Suborder-Haplorhini Infra-order-Simiiformes Parv-order-Catarrhini Superfamily-Hominoidea

Hominines (Hominids)All species believed to be more closely related to human than

chimpanzeesHumans and our direct ancestors, since the split from

chimps.Major groups:

Australopithecines Paranthropsus Homo genus

Chimps are not ancestral species !! We shared a common ancestor.

Not a direct line to us !! A radiating lineage. Several hominids species co-existed.

Gorillas, chimps and hominids split about 6-8 MYA. At a generous 25 year generation time: 320,000 generations ago with strong natural selection

SKULL EVOLUTION

Chromosome ABNORMALITY: A chromosome abnormality or mutation is a missing, extra, or

irregular portion of chromosomal DNA . It can be from an atypical number of chromosomes or a structural abnormality in one or more chromosomes. 

Chromosome mutation was formerly used in a strict sense to mean a change in a chromosomal segment, involving more than one gene .

 A karyotype refers to a full set of chromosomes from an individual that can be compared to a "normal" karyotype for the species via genetic testing. A chromosome abnormality may be detected or confirmed in this manner.

Chromosome abnormalities usually occur when there is an error in the cell division following meiosis or mitosis. There are many types of chromosome abnormalities. They can be organized into two basic groups, numerical and structural anomalies.

Other extant hominids have 2n=48. Hominids (at least humans) have 46.

Hominid life on ground:Bipedalism, upright walking Jaw shape -smaller with specialized teeth with an

omnivorous diet. Pronounced chin. larger brain size, increased cerebrum, by paedogenesisReduced size difference between sexes tool use, language, social behaviorExtended parent care time- longer juvenile periodMore learningReduced sense of smell Increased size of brain for vision and co-ordination with

musclesEyes are larger and directed forward

Sahelanthropus tchadensis

Sahelanthropus tchadensis is an extinct homininae species.Dated to about 7 million years ago, possibly very close to the time of the chimpanzee-human divergence.The fossils were discovered in the Diurab Desert of Chad in central Africa.

Orrorin tugenensis Dates to 6.1-5.8 MYA Discovered in 2000 Thought to be in evergreen forest, not open

grassland Oldest bipedal fossils Fossilized bones from 5 individuals Only a few femurs and teeth.

Orrorin tugenensis

Teeth

Neck bones

Leg bones

AustralopithecusFirst “humans”:

Australopithecus, about 4.4Million years ago Walked fully upright

with humanlike teeth and hands. Fossil evidence of

hip, hands. Skull, capacity about 1/3

modern human size. lasted 3 Million Years. All fossils from Eastern

and Southern Africa

Homo ergaster

Less sexual dimorphism, more pair bonding

Larger brainSlender legs, distance walkingShort straight fingers. No longer

climbing treesSmaller teeth, foods more prepared

less hard chewingMore advanced toolsMore habitats1.9 - 1.6 Million Years Ago

Homo erectusHomo erectus was the first to migrate out of

Africa into Europe and Asia. Java man and Peking man are Homo erectus. H. erectus 1.8 million years ago - 300,000

years ago. gave rise to larger populations, had to

continually expand to find food, hunt farther out.

Homo heidelbergensisDescended from H. ergaster in africa, spread

out.Northern populations in Europe under ice age

conditions became The Neanderthals 200,000 -40,000 years ago in Europe

Reaming population in Africa adapted to drought conditions, became homo sapiens, spread out to rest of world.

Homo neanderthalensis

The Neanderthals 200,000 -40,000 years ago in

Europe Brain as large or larger than

present day humans Buried their dead Made hunting tools from stone

and wood Carnivorous

Homo sapiensTwo models for the origins of

anatomically modern HumansMulti regional model has

interbreeding among the different H. erectus groups and a common origin for Homo sapiens on the different continents.

Homo forensicDiscovered in 2003Lived until as recently as 18,000

years agoVery small- Island effect

Pygmy elephantsDescent from larger H. erectus

Oldest Homo sapiens fossil

SKULL GALLERY………..