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Slide 1

The Origin of Our Own Species

Slide 2

Primates

• Primates -mammals adapted for tree-dwelling lifestyles

• Typically:

• Large brains

• Large eyes

• Binocular vision

• Grasping hands

Grey-shanked douc langur (Pygathrix cinera)

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Slide 3

Primate Members

• Lemurs

• Lorises

• Tarsiers

• Monkeys

• Great apes

• Humans

Slide 4

Primate History

• earliest primates first appeared ~about 55 my ago

• Two distinct characteristics:

• grasping hands and/or feet with opposable thumbs

• Binocular vision

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Slide 5

Primate Binocular Vision

• binocular vision primate eyes shifted to front of face. Allows visual fields from both eyes to overlap for 3D vision = better depth/distance perception

Slide 6

Primates as prosimians

• The first primates are often called prosimians or "before monkeys“

• Only a few prosimians survive today

• Lemurs

• Tarsiers

• Lorises

Western tarsier

Ring-tailed lemur

Slow lorise

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Slide 7

Prosimians on Madagascar• Most (but not all) prosimians found on the island of

Madagascar• All lemur species are found there

• grave concern is rapid destruction of forest habitat in Madagascar

• Its destruction will mean extinction for the lemurs

Slide 8

Primate History• ~ 40 my ago, primates switched from nocturnal lifestyle (night life) to

diurnal lifestyle (active during the day)

• These new primates evolved from prosimian ancestors and eventually evolved into the New World and Old World monkeys

• The switch to daylight living might have influenced improvements in primate eye (Cones developed in the retina and color vision developed)

– additional demands of color vision and perception require a larger brain!

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Slide 9

Primate Thumbs for Grasping

• The opposable thumb became well developed in the monkeys

Slide 10

Monkeys Old & New

• New World Monkeys -South America and Central America

• All other monkeys are called Old World Monkeys (include monkeys in Africa and Asia)

Brown spider monkey

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Slide 11

About New World Monkeys

• New World monkeys have broad noses

• Most are strictly arboreal (live in trees) and have prehensile (grasping) tails Emperor tamarin

Woolly monkey

Slide 12

Who are New World Monkeys?

• New World monkeys include:

– Marmosets

– Squirrel monkeys

– Capuchins

– Spider monkeys

– Howler monkeys

Capuchin monkey

Squirrel monkeyMarmoset monkey

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Slide 13

Old World Monkeys

• Old World monkeys have narrow noses

• live in a diversity of environments

• Some are arboreal, others more terrestrial

Olive baboon

Slide 14

Who are Old World Monkeys?

• Old World monkeys include:

– Guenons

– Baboons

– Leaf monkeys

– Macaques

• More closely related to the great apes than New World monkeys

Crab-eating macaque

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Slide 15

Apes

• ~25 my ago, a different type of primate evolved – the apes

• Apes larger brains than monkeys, no tails

• found in Africa and Asia

• No apes or ape fossils found in North or South America

Western lowland gorilla

Slide 16

Gibbons – lesser apes

• Gibbons - often called lesser apes because they are smaller, have less complex social behavior, and anatomical characteristics different from other apes

Lar gibbon

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Slide 17

Great Apes

• All other apes called Great Apes

• Four living types of great apes:

• Orangutans

• Gorillas

• Chimpanzees

• Humans

Bornean orangutan

Slide 18

Primate EvolutionFrom molecular studies:• evolutionary pathway to gibbons split off from the basic ape line

~15 MYA • orangutan line split off ~13 MYA • gorilla line split off ~MYA

(fancy cladogram!)

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Slide 19

Primate Evolution & Taxonomy

• split between chimpanzee line and human line ~6-8 MYA

• look at our taxonomy

DOMAIN: Eukarya

KINGDOM: Animalia

PHYLUM: Chordata

SUBPHYLUM: Vertebrata

CLASS: Mammalia

ORDER: Primates

Slide 20

Monkeys Orangutans Gorillas Chimpanzees Humans

Order Primates Primates Primates Primates Primates

Family + Hominidae Hominidae

Hominidae Hominidae

Subfamily + Ponginae Homininae

Homininae Homininae

Tribe Gorillini Hominini Hominini

Subtribe Hominina

Genus + Pongo Gorilla Pan Homo

Species + * * * Homo sapiens sapiens

+ too many to include here* Genera Pongo, Gorilla and Pan each include several living species

The Taxonomy – How Humans fit in…(compare Humans with Chimps)!

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Slide 21

Genus HomoTerminology

• The word “human” used to refer to any member of the genus Homo

• We are members of that genus, classified as Homo sapiens sapiens, the only living species left in the genus (all other species in genus Homo are extinct!)

• Distinctions within the group “human” aremade using species names– Homo habilis

– Homo sapiens

– Homo erectus

• “Modern humans” = Homo sapiens sapiens

Slide 22

Genus HomoTerminology (cont…)

• The word hominid is convenient but ambiguous

• It is derived from the family name Hominidae(from human taxonomic classification)

• Living members of Family Hominidae include humans, chimpanzees, gorillas, and orangutans

Common chimpanzee

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Slide 23

Genus HomoTerminology - homonid (cont…)

• Many extinct species in Family Hominidae, some on same branch as humans, some on branches that terminate at other living members

• Hominid is ambiguous because it has no standard meaning• Our definition (for convenience): a hominid is any member of genus

– Ardipithecus (Ethiopia, ~4.4 MYA, upright, oldest?)– Australopithecus (Eastern Africa, ~4 MYA, “Lucy”) – Kenyanthropus (East Africa, ~3.5 MYA, flat face, small cranium, strong

mastication)– Paranthropus (Olduvai Gorge, Tanzania, ~2.7 MYA, Mary Leakey,

robust, canines & incisors similar to humans, extra tough postcanines– Homo – see next slide…

Slide 24

Genus Homo- the Members (from http://archaeologyinfo.com/genus-homo/)

http://archaeologyinfo.com/genus-homo/

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Slide 25

Genus HomoTerminology

• These are all known genera that arose since we split away from chimpanzees

• timing of split cannot be exactly known

• assume that it occurred ~7 mya

Bonobo

Slide 26

Human Evolution Hypotheses –not easy

• all classification schemes are artificial make arbitrary decisions about grouping organisms

• process is much more difficult with fossils because no additional information from DNA, living tissue, and behavior like used to classify living species

• Putting together a picture of human history from fossils is like assembling a jigsaw puzzle that has many, if not most, of the pieces missing… : /

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Slide 27

Human Evolution Hypotheses & New Discoveries

• Every new fossil might allow rejecting some existing hypotheses, or allow new ones

Slide 28

Human Evolution Hypotheses -Historically

• At one time, human fossil history was interpreted as a simple progression from one form to another, with anatomically modern humans at the end

• So, the hypothesis describing human evolution appeared like this

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Slide 29

Human Evolution Current Hypothesis

• The current hypothesis is different, including as many as five different genera:

– Ardipithecus

– Australopithecus

– Paranthropus

– Kenyanthropus

– Homo

Ardipithecus ramidus specimen

Slide 30

Human Evolution Hypothesis-complex

• multiple species within each genus

• relationships between these organisms are not clear-cut -Lots of side branches

• Humans at the end of the only branch that survived!

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Slide 31

Human Evolution Hypothesis- relative ancestors

• Australopithecus considered to be ancestor of Homo habilis

• Homo habilis ancestor of Homo erectus

• Homo erectus ancestor of Homo sapiens

Australopithecus afarensis

Slide 32

Human Evolution Hypothesis-Homo sapiens

• Homo sapiens had two different sub-species:

– Homo sapiens sapiens

– Homo sapiens neanderthalensis

Homo sapiens neanderthalensis

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Slide 33

Human Evolution Hypothesis – 2 genera

• Originally, the species were divided into two genera

– Small-brained but bipedal Australopithecus

– Big-brained, tool-using Homo

Slide 34

Human Evolution Hypotheses

• One of the other four genera is most likely the direct ancestor of Homo and the best bet right now is Australopithecus

• New evidence constantly shifts relationships around on the evolutionary tree A. afarensis

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Slide 35

Human Evolution Hypotheses

• There are newly described Homo species (won’t discuss here) that are not yet universally accepted

• This field is controversial, and ongoing discussion and new finds will change the story

Homo rhodesiensis (Rhodesian man)

Slide 36

Hominid Characteristics

• All hominids are bipedal and have larger brains than the non-human apes

– “larger brain” = relative brain size (ratio of brain to body size)

– Hominids have a larger brain relative to their body size compared to non-hominid apes

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Slide 37

Hominid Characteristics -Bipedalism

• Bipedalism structural changes skeleton, muscles and nervous system (necessary for walking on two legs)

– Bipedalism in hominids probably evolved about 4 MYA

Slide 38

Characteristics of Humans

• Humans = group of hominids that share hominid characteristics plus tool use and larger relative brain size

– Remember: all humans are hominids but not all hominids are humans

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Slide 39

Evolutionary History of Humans

• One of the earliest hominid genera is Australopithecus

• There are at least five species of Australopithecus known from fossils

A. africanus

Slide 40

Australopithecus

• The oldest is over 4 million years old and several are as recent as 2 million years old

• Their fossils show that these species walked upright, their teeth are more human-like than ape-like, and their brain capacity is about 1/3 the size of Homo

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Slide 41

Homo habilis

• The first human probably evolved from an Australopithecus ancestor about 2 MYA

• These first humans were named Homo habilis or "handy man" because tools were found with the fossils

Slide 42

Homo habilis (cont…)

• oldest Homo habilisfossils are ~ 2 my old but fossil tools date to 2.5 MYA, implying either Homo habilis was around by 2.5 MYA OR there is another tool-making genus whose fossils have not yet been found

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Slide 43

Homo habilis (cont…)

• Homo habilis fossils reveal brain capacity ~ ½ the size of modern humans (Homo sapiens sapiens)

• Homo habilis lived in Africa for about 500,000 years before becoming extinct

Slide 44

Homo erectus

• next species to evolve on the Australopithecus-Homo branch = Homo erectus ("erect man" / "man who walked upright")

• After Homo erectus was found and named, other erect, bipedal hominid fossils were found, but species names didn’t change

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Slide 45

Homo erectus (cont…)

• Homo erectus walked upright, was about 5-6 feet in height, and had a larger brain than previous species (about 2/3 the size of modern humans)

– A skull with prominent brow ridges

– Rounded jaw

Slide 46

Homo erectus (cont…)

• Homo erectus fossils dated at ~1.8 my

• Apparently evolved in Africa and spread quickly throughout Asia and Europe

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Slide 47

Homo erectus (cont…) – living info

• They lived in small social groups

– Used flint and bone tools

– Lived in caves or crude wooden huts

– Hunted animals

Slide 48

Homo erectus - disappears (cont…)

• Homo erectus is the first human (in the fossil record) to demonstrate the use of fire

• In Africa, Homo erectus disappeared about 500,000 years ago

– In Asia, Homo erectus disappeared about 80,000 years ago

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Slide 49

Homo sapiens

• The oldest fossils of Homo sapiens (“wise man”) are ~ 500,000 years old

• similar to modern humans (Homo sapiens sapiens) but anatomical differences:

– Larger teeth

– Prominent brow ridges

Slide 50

Homo sapiens neanderthalensis

• At the same time, their brain size is significantly larger than Homo erectus, approaching the average of modern humans

• In Europe and Asia, archaic humans evolved into Neanderthals (Homo sapiens neanderthalensis)

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Slide 51

Homo sapiens neanderthalensis(cont…)

• oldest Neanderthal fossils ~ 130,000 years old

– short powerful bodies

– Massive skulls with heavy brow ridges above eyes

• Interestingly, brains were larger than modern humans

Slide 52

Homo sapiens neanderthalensis(cont…)

• made many tools, including axes and spearheads

• Cared for injured and elderly

• Buried their dead, placed flowers in the graves, (some controversy about this interpretation…)

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Slide 53

Homo sapiens neanderthalensis(cont…)

• By ~ 100,000 years ago, common throughout Europe, Asia and near East

• Body changes in Neanderthals appear to in response to the cold climate of the Ice Ages

• Neanderthals extinct by 30,000 years ago

Slide 54

Homo sapiens sapiens

• Homo sapiens sapiensfirst appeared in Africa more than 120,000 years ago

– Made beautiful stone tools

• By 30,000 years ago, they spread out of Africa everywhere except the Americas

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Slide 55

Homo sapiens sapiens (cont…)

• The fossil evidence is backed up by molecular evidence based on mitochondrial DNA

Slide 56

Homo sapiens sapiens –the Cro-Magnons (cont…)

• arrived in Europe ~35,000 years ago

• Early European Homo sapiens sapiens often called Cro-Magnons

• discovered in Les Eyzies de Tayac –Dordogne – France in 1868

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Slide 57

Homo sapiens sapiens –Cro-Magnon

• Cro-Magnon used sophisticated stone, bone and horn tools

• They had a complex hunter-gatherer society

Slide 58

Homo sapiens sapiens –Cro-Magnon paintings

• responsible for cave paintings found throughout Europe

• Evidence that Cro-Magnons used symbolic language

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Slide 59

Neanderthal Extinction

• extinction of Neanderthal Homo sapiens is interesting to scientists

• Based on fossil, archeological, and DNA evidence, some think that they interbred with Cro-Magnons and so they were genetically “absorbed” into the other species

Slide 60

Neanderthal Extinction

• Another hypothesis was they were killed off by diseases brought by the rapidly spreading Cro-Magnon– Little evidence to

support this

– Both Neanderthals and Cro-Magnon coexisted for several thousands of years in some places

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Slide 61

Neanderthal Extinction

• A third hypothesis is that Cro-Magnons were better competitors for food and shelter and gradually replaced Neanderthals throughout their range

Slide 62

Neanderthal Extinction

• A fourth hypothesis is based on differences in migration patterns between Neanderthals and Cro-Magnons

• A fifth hypothesis is that Cro-Magnons deliberately killed off Neanderthals

• Also questionable because they lived in the same areas for thousands of years

• Recent research has been able to compare the DNA of Neanderthals to the DNA of modern humans

– May help eliminate some of these hypotheses

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Slide 63

Neanderthal Extinction

• The DNA comparisons show that 1-4% of the genes on non-African modern humans appear to be inherited from Neanderthals

• This means that, in Europe, Neanderthals and modern humans probably interbred

• This makes it unlikely that Cro-Magnons killed off the Neanderthals, either deliberately or through diseases

• This may be evidence that supports the first or third hypotheses

Slide 64

Advance of Humans