Hominid Evolution

• Hominids family of organism that includes humans

• Earliest subgroup of primates– FAMILY is a classification level between

ORDER and GENUS

• First appeared between 6 and 7 million ears ago

• Has evolved several times..we can tell by looking at fossil evidence…Skulls in particular

Hominid Evolution

• Today researchers believe Hominid evolution proceed by:– Adaptive radiation is a process by

which a several species evolve from single ancestral species.

Hominid Evolution

Hominid Evolution• Appearance, behavior, and

anatomy changed in early humans…

• Adaptations in hominid evolution include:

1. Bipedal locomotion-walking upright on 2 legs

2. Large brains- specially cerebrum; Increase in cranial capacity

3. Changes in skull shape, including decrease in size of brow ridge (section of bone above eye)

4. Decrease in jaw size and angle at which jaw protrudes from face

5. Decrease in the number of teeth and tooth size

6. Opposable thumbs- adapted for grasping

7. Development of the ability to make and use tools

8. Development of the ability to communicate using language

Early Hominids• Ardipithecus kadabba earliest known

hominid species discovered on 2001– Lived 5.8-5.2 million years ago

• Earliest group of hominids: Australopithecines

• Australopithecus, means "southern ape”• Believed to exist from about 4 million

years ago until about 1 million years ago• Australopithecus afarensis

– First fossils discovered in the Afar region of Africa

– Species existed between 3 million and 4 million years ago

– A. afarenis was shorter than modern humans, less than 1.5 m tall

– “Lucy” are the best-known fossils of A. afarensis discovered in 1974• Most complete fossil set of this hominid• About 3.5 million years old• Found near fossilized set of footprints• Evidence suggest bipedalism

Fossilized A. afarensis tell

us:• Early hominids had small cranial

capacity of 400 cm3 (small brain)– Bipedalism occurred BEFORE large

brains evolved– HOMINIDS were walking on 2 feet

and had small brains

• Early hominids were not very tall

• Early hominids had large brow ridge

• Early hominids had Large, angular jaw that jutted out from face

2 more species of Australopithecus found in Africa:

• Australopithecus africanus– Lived about 2.7 to 2.1 million years ago– Humanlike hands– Walked upright– Cranial capacity of about 500 cm3

• Australopithecus robustus– Lived about 2.1 to 1.4 million years ago– “robust” because it had a heavier bone structure

than A. africanus– Larger cranial capacity (550 cm3)…about 1/3 of

the average for the modern human brain– Larger teeth– Less protruding jaw than earlier hominids

Another Discovery…

• 2008/2009• Team of scientists discovered fossilized remains

of portions of two hominid skeletons between 1.78 and 1.95 million years old in a South African cave– First Skelton and skull of 11-12 year old boy, about

130 cm tall and cranial capacity of 420 cm3 – Second Skelton of adult female

• Designated Australopithecus sediba• Analysis suggests that they probably desended

from A. africanus• BUT Some scientists believe that remains

represent an early member of the genus Homo

First Hominid in genus Homo: Homo habilis

• Earliest Hominid fossils considered genus Homo discovered in 1964 by Louis and Mary Leaky

• The Leakys also found simple stone tools with fossils

• They inferred that these hominids used tools• Homo habilis means “handy man”• These fossils were 2 million years old• Existed same time as Australopithecus

robustus– Co-existed for a little less than 1 million years– Evolved at the same time

Major Differences Between H. habilis and A. robustus

Homo habilis• Smaller brow ridge• Large cranial

capacity (650 cm3…half of the size of the modern human brain)

• First hominid associated with tool use

Australopithecus robustus• Larger brow ridge• Smaller cranial

capacity (550 cm3)

New Species: Homo erectus

• Appeared after H. habilis and A. robustus• Means “upright human”– Walked fully upright on 2 legs

• Earlier hominids may have been able to walk on 2 legs but they also knuckle-walked and swung from tree limbs

– Discovered and named BEFORE “Lucy” A. afarensis was discovered• Remember she was the earliest bipedal hominid

• existed from about 1.6 million years until about 200,000 years ago

• Large Cranial capacity of 1000 cm3…half • This hominid was much taller than H. habilis

and had much smaller teeth than H. habilis

Homo erectus facts:

• Evidence suggests these hominids lived in small groups– Indicates they may have used

some sort of language– Throats and mouths could not

make complex sounds in modern human language though

• Made tools of both stone and bone

• Evidence suggests they used fire

• May have cooked their food

Homo sapiens

• Most modern species of humans• Means “wise human”• Likely arose from H. erectus about

100,000 to 200,000 years ago• Controversy!– Some scientists believe that H. sapiens

evolved DIRECTLY from H. erectus– Other scientists believe that H. sapiens

evolved from Homo neanderthalensis (Neanderthals), who evolved from Homo erectus

Proposed evolution of modern Humans!!!Homo habilis

H. erectus

H. neanderthalus

H. sapiens

H. Erectus

H. sapiens

???

Homo neanderthalensis (Neanderthals)

• Emerged in Germany about 300,000 years ago• Lived until about 30,000 years ago• Made and used tools• Lived in organized societies• Had brains similar in size to modern humans• Large brains + organized society = more

advanced language skills than earlier hominids• DNA from Neanderthals is 99.7% identical to

modern humans• Many modern ethnic groups show traces of

Neanderthal DNA in their genome – Genome- all the hereditary information of an

organism, including sequences of bases in its DNA and the positions of genes on its chromosomes

H. Sapiens & Neanderthals Mixing

• About 40,000 years ago, H. sapiens were physically similar to modern humans

• Lived close to Neanderthals in some places

• Some scientists believe that living near eachother enabled GENE FLOW between the H. sapiens and the Neanderthal populations

How did modern humans come to be?

• Humans 40,000 years ago had sophisticated language skills

• Over the next 20,000 to 30,000 years they developed more complicated and useful tools

• Between 20,000 and 30,000 years ago, humans started to create art

• Around 10,000 years ago humans learned

to grow crops instead of relaying solely on hunting and foraging.

• Homo habilis-– Oldest…existed 2 million years ago– handy man.” fossils found with tools

• Homo erectus means upright human– Existed 1.6 million years ago to about 200,000 years ago– Taller and larger brain than Homo habilis– Smaller teeth than Homo habilis– Lived in groups (suggest language use) and used fire

• Homo sapiens- means wise human– Existed about 100,000 to 200,000 years ago– Some believe they arose directly from Homo erectus while other believe they

arose from Homo Neanderthals (who descended from Homo erectus)– By about 40,000 years ago, H. sapiens were physically identical to modern

humans

• Homo neanderthalensis - Neanderthals – Emerged in Germany 300,000 years ago– Lived till about 30,000 years ago– made stone tools and lived in organized social groups and had

organized societies– Brain was similar in size to modern humans– DNA evidence now supports this theory…modern human DNA is

99.7 % identical to that of the Neanderthals• Cro-Magnons appeared in Europe (shortly after, Neanderthals

disappeared) • Modern Humans –Last 10,000 years, Earth’s only hominid.