HUMAN

Where did we come from?

www.christs.cam.ac.uk/darwin200

EVOLUTION

HUMAN EVOLUTIONDarwin & Human evolution

Darwin was very aware of the implications his theory had for humans.

He saw monkeys during the Beagle voyage but saw his first Ape at London Zoo.

Darwin first saw Jenny the Orang-utan in 1838;He recognized human-like qualities in her

HUMAN EVOLUTIONDarwin & Human evolution

Darwin was very aware of the implications his theory had for humans.

He saw monkeys during the Beagle voyage but saw his first Ape at London Zoo.

Darwin first saw Jenny the Orang-utan in 1838;He recognized human-like qualities in her

Even Queen Victoria recognized the similarities:

HUMAN EVOLUTIONDarwin & Human evolution

Darwin was very aware of the implications his theory had for humans.

He saw monkeys during the Beagle voyage but saw his first Ape at London Zoo.

“frightful and painfully and disagreeably human.”

HUMAN EVOLUTIONDarwin & Human evolution

But the only mention of human evolution in On the Origin of Species (1859) was:

“Light will be thrown on the origin of man and his history”

Darwin left people to figure it out the implications ofhis work themselves

HUMAN EVOLUTIONDarwin & Human evolution

He later dealt with the topic more thoroughly in The Descent of Man (1871)

• comparisons between apes & humans reveal their shared ancestry

• Darwin also showed all human races were onespecies (which was debated at the time)

• Also outlined his theory of sexual selection

HUMAN EVOLUTION

sapiens

Homo

Hominidae

Primates

Mammalia

Chordata

Animalia

Eukaryota

Human classification

HUMAN EVOLUTION

sapiens

Homo

Hominidae

Primates

Mammalia

Chordata

Animalia

Eukaryota

Human classification Characteristic features:

“thinking man”

Man: bipedal

The apes; no tails, larger bodies

Large brains, stereoscopic vision

Have mammary glands

Develop dorsal nerve cord

Multicellular, heterotrophic, no cell walls

Cells with membrane bound nucleus

HUMAN EVOLUTION

Humans are primates.

Primates are distinguished from other mammals by:

· greater reliance on vision than smell

· shortened snout

· grasping hands & feet

· nails instead of claws

· large brains relative to body size

What are the main characteristics of primates?

HUMAN EVOLUTIONWhat are the main characteristics of primates?

Primates evolved 70-80 million years ago.There are about 600 living species.

25% are endangered!

Humans are primates.

Primates are distinguished from other mammals by:

· greater reliance on vision than smell

· shortened snout

· grasping hands & feet

· nails instead of claws

· large brains relative to body size

HUMAN EVOLUTIONYou are here

The primate family tree

Ring tailed lemur

Tariser

Slow Loris

Woolly monkey

Mandrill

Gorilla

HUMAN EVOLUTIONThe Apes

HumansHomo

Orang-utan Pongo

ChimpanzeesPan

GibbonsHylobatidae

GorillasGorilla

Who is more closely related to who?

HUMAN EVOLUTIONThe Apes

HUMAN EVOLUTIONThe Apes

HUMAN EVOLUTIONThe Apes

HUMAN EVOLUTIONThe Apes

Which is more closely related to chimpanzees:

humans or gorillas?

HUMAN EVOLUTIONThe Apes

Which is more closely related to chimpanzees:

HUMANS!

This grouping is supported by

anatomical and DNA evidence

HUMAN EVOLUTIONHow do humans and chimpanzees differ?

HUMAN EVOLUTION

Brain sizeBody hair

Face lengthLocomotion

How do humans and chimpanzees differ?

HUMAN EVOLUTION

Brain sizeBody hair

Face lengthLocomotion

How do humans and chimpanzees differ?

Brain size 1300-1400g 400gBody hair not much quite a bitFace length shorter longerLocomotion bipedal knuckle walking

HUMAN EVOLUTION

5-7 million years ago5-7 million years ago

virtually no chimpanzee fossils

Lots of hominid (human ancestor)

fossils

How did these difference evolve? Evidence from fossils

The human fossil record is quite good – about 20 species are recognised.The chimpanzee fossil record is very poor.

HUMAN EVOLUTION

Paleo-anthropologists don’t always agree on the proposed relationships among the early human ancestors

But we can recognize general trends

The human fossil record

HUMAN EVOLUTION

There was not a directed, gradual progressionbut instead a mosaic pattern

The human fossil record

HUMAN EVOLUTION

Increase in brain size

EvolutionBipedalism

Reduction in face more gradual

The human fossil record

HUMAN EVOLUTIONThe human fossil record

HUMAN EVOLUTION

Increase in brain size

Bipedalism

Reduction in face more gradual

The human fossil record

HUMAN EVOLUTION

Darwin predicted this long before man’s African origins were established:

“In each great region of the world the living mammals are closely related to the extinct species of the same region. It is therefore probable that Africa was formerly inhabited by extinct apes closely allied to the gorilla and chimpanzee; and as these two species are now man’s nearest allies, it is somewhat more probable that our early progenitors lived on the African continent than elsewhere.-Darwin (1871) The Descent of Man

Modern humans evolved in Africa

HUMAN EVOLUTIONModern humans evolved in Africa

The oldest known fossils of anatomically modern humans were found in Ethiopia from about 150,000 years ago

HUMAN EVOLUTIONModern humans evolved in Africa

The oldest known fossils of anatomically modern humans were found in Ethiopia from about 150,000 years ago

Most scientists agree Homo sapiens evolved in Africa and migrated out from this single origin

HUMAN EVOLUTIONModern humans evolved in Africa

Most scientists agree Homo sapiens evolved in Africa and migrated out from this single origin

This is supported by genetic and phenotypic evidence. The diversity of both decrease with over-land distance from Africa.

This is what would be expected if humans evolved once and their range expanded, going through a series of population bottlenecks

HUMAN EVOLUTIONWhat does the DNA evidence say?

Scientists have now sequenced the genome of a:• Human• Chimpanzee• Gorilla• Orang-utan • Gibbon• Macaque (an old world monkey)• Marmoset (a new world monkey)• and a type of galago and a lemurAs well as many other mammals!

The DNA evidence confirms the relationships between humans, primates and other mammals.

They show how similar we are, genetically, to chimpanzees:• an estimated 96-98% of our DNA sequence is identical to chimpanzees• (but that’s still millions of differences!)

HUMAN EVOLUTIONWhat does the DNA evidence say?

By comparing the DNA sequences biologists can see which regions of the genome have changed rapidly since the human-chimpanzee split.

These studies highlight genes involved in:• immunity & defence – evolving to tackle new diseases as humans spread• digestion – evolving as human diets changed in different environments • brain development – potentially having roles in the expansion of the human brain

HUMAN EVOLUTIONWhat does the DNA evidence say?

By comparing the DNA sequences biologists can see which regions of the genome have changed rapidly since the human-chimpanzee split.

These studies highlight genes involved in:• immunity & defence – evolving to tackle new diseases as humans spread• digestion – evolving as human diets changed in different environments • brain development – potentially having roles in the expansion of the human brain

BUT…

There is still a lot about the genetic basis of human evolution to understand.

Linking genetic changes to the evolution of human traits is a challenging task!

www.christs.cam.ac.uk/darwin200For further information visit:

HUMAN EVOLUTIONCONCLUSIONS:

• humans belong to a group of mammals called primates

• our closest living relative is the chimpanzee, our evolutionary paths separated 5-7 million years ago

• the human fossil record is quite good and reveals how and when ‘human traits’ evolved

• modern humans evolved in Africa and migrated around the world

•DNA evidence supports these conclusions and is beginning to reveal changes in genes important to human evolution