Tracking Human Evolution:Where Do We Fit on the

Tree of Life?

Geology 230

Fossils and Evolution

Amniotahttp://tolweb.org/Amniota/14990

Crocodiles

hatching from

their amniote

eggs

Pennsylvanian

anapsid or

stem reptile

Amniote Family Tree

Prothero, 2007

Synapsid Skull: one opening behind the orbit (eye)

Diapsid Skull: two openings behind the orbit (eye)

Synapsidahttp://tolweb.org/Synapsida/14845

Permian Synapsids, Germany

Triassic synapsid reptiles: Therapsids or

mammal-like reptiles

Therapsida, Mammals and extinct relatives http://tolweb.org/Therapsida/14973

BiarmosuchiaEotitanosuchiaDinocephaliaAnomodontiaTheriodontia

GorgonopsiaTherocephaliaCynodontia

DiviniidaeMammaliaProcynosuchidaeGalesauridaeThrinaxodontidaeCynognathidaegomphodontsChiniquodontidaeProbainognathidaeTritheledontidae (Ictidosauria)

A Gallery of

Therapsids

Carl Buell

From Synapsids to Mammals, a well documented transition series

Prothero, 2007

Prothero, 2007

Multiple bones in the lower jaw of the dino T. rex.

Yanoconodon, Lower Cretaceous Mammal from China

Yanoconodon, Lower Cretaceous of China, retains ear bones attached to inside lower jaw

Morganucodon

Yanoconodon

Human Ear Bones,

or Auditory Ossicles

Cochlea

Mammaliahttp://tolweb.org/Mammalia/15040

Class Mammalia - Late Triassic to RecentSuperorder Tricodonta - Late Triassic to Late

CretaceousSuperorder Multituberculata - Late Jurassic to

Early OligoceneSuperorder Monotremata - Early Cretaceous

to RecentSuperorder Metatheria (Marsupials) - Late

Cretaceous to RecentSuperorder Eutheria (Placentals) - Late

Cretaceous to Recent

Evolution of Mammalian Superorders

Eutheria

(Placentals)

Metatheria

(Marsupials)

Live Birth

Mammary Glands?.

.

Monotremes

..

Extinct: U

Mammals in the Age of Dinosaurs

Hadrocodium, a lower Jurassic

mammal with a “large” brain (6 mm

brain case in an 8 mm skull)

Lower Cretaceous mammal from China

Jawbones of a Cretaceous

marsupial from Mongolia

Mammal fossil

from the

Cretaceous of

Mongolia

Repenomamus robustus

fed on psittacosaurs.

Image: Xu Xiaping, 2005

Early

Cretaceous

mammal ate

small

dinosaurs

Repenomamus robustus

Repenomamus robustus

with psittacosaur in the

gut

Modern Elephant Shrew

Weasel hunting

at night

Bats, such as this vampire bat,

hunt at night

Monotremes: Platypus

The Platypus baby

adult

egg

Monotremes: Echidna

The Echidna

Typical

Marsupial, a

Kangaroo

Poorly developed

newborn

kangaroo

attached to a

nipple in the

pouch.

Eutheriahttp://tolweb.org/Eutheria/15997

Primate Classification- 1980’s

Order Primates

Suborder Prosimii: tarsiers and lemurs

Suborder Anthropoidea: monkeys, apes, and hominids

Superfamily Hominoidea

Family Pongidae: great apes

Family Hominidae: Homo and hominid ancestors

Primate Classification – 2000’sOrder Primates

Suborder Prosimii: tarsiers and lemurs

Suborder Anthropoidea: monkeys, apes, and

hominids

Superfamily Hominoidea

Family Hominidae: all hominoids

except gibbons

Subfamily Ponginae: orangutans

Subfamily Homininae: gorillas, chimps,

Homo and hominin ancestors

98%

96%

95%

91%

84%

58%

100%% genetic similarity with humans

Prothero, 2007

Tarsiers, a primitive

Primate (Prosimian)

from Southeast Asia.

Tarsier sanctuary, Philippines

A Galago or bush

baby, a primitive

Primate

(Prosimian) from

Africa.

A Slow Loris, a

primitive Primate

(Prosimian) from

Southeast Asia.

Check out the

fingers.

Lemurs, primitive Primates

(Prosimians) from Madagascar.

Monkeys, such as baboons, have tails

and are not hominoids.

Proconsul, the oldest hominoid, 18 MY

Hominoids

The Orangutan, a Great Ape from Southeast Asia.

Gorillas, Great Apes from Africa.

Chimpanzees, Great Apes from Africa.

I’m cool

Neoteny in Human Evolution. Humans

resemble baby apes more than adult

apes. Humans are said to be

paedomorphic.

Chimp skull on the left, human skull on the right

Chimp

Homo sapiens

Consequences of Neoteny

• Large brain and cranium

• Small jaws and teeth with small face

• Retention of juvenile growth patterns

• Long juvenile period = extended learning

• Retardation of onset of puberty

• Longer life span

• Naked skin

Next: The Hominid Fossil Record