Class Notes (809,049)
Canada (493,506)
Biology (2,348)
BIOLOGY 1M03 (663)
Jon Stone (82)

1MO3_Chapter 10.docx

4 Pages
Unlock Document

McMaster University
Jon Stone

From Hominoid to HomininDuring the Miocene the Earths temperature began to fall This global cooling caused two important changes in the climate of the African tropicso The total amount of rain that fell each year declined o Rainfall became more seasonal so there were several months each year when no rain fellAs the tropical regions of Africa became drier moist tropical forests shrank and woodlands and grasslands expanded Changes brought about through generations of natural selection allowed a few species to move down from the trees out of the rain forests and into the woodlands and savannahsHominins Six mya climate and geographic change led to the evolution of hominins oCooling less rain rain seasonality woodland and savannah spreadThese creatures were different from any of the Miocene apes in two wayso First and most important they walked upright This shift to bipedal locomotion led to major morphological changes in their bodies and new food became availableo Second some of the hominin species began to exploit new savannah and woodland habitats and new kinds of food became available As a result of the hominin chewing apparatusincluding many features of the teeth jaws and skull changedWhat is Unique about UsWe walk on two legs bipedalismWe have small canines and large molars with thick enamelWe have large brains in relation to our body size We have very slow life histories and a long juvenile period We talk and have elaborate symbolic cultureWhat It Takes to Be a BipedSkull o Foramen magnum positionSpineo Lumbar lordosisPelvis o Short and stout in a biped o Abductor mechanismFemur o Long femoral neck o Cortical bone distributionKnee o Bicondylar angleFoot and ankle o Nongrasping big toe o Arches First HomininBetween 75 mya the common ancestor of chimps and humans roamed the earthSahelanthropus tchadensis discovered in 2002 I the earliest known hominin living around 76 mya It has both derived and ancestral traitsAt the Beginning Sahelanthropus Genetic data indicate that the last common ancestor of humans and chimpanzees lived between 7 5 myaSahelanthropusChad AfricaIs the earliest known hominin has a surprising mix of derived and primitive featuresThe fossil material consists of a nearly complete cranium skull minus the lower bone four partial mandibles and four teeth This fossil shook up the paleontological community because of its age and location Represents the oldest known hominin 67 million years oldHominin o Foramen magnum the hole in the skull through which the spinal cord passes is located under the skull rather than at the back suggests bipedalism o Chimpanzeesized brain o Small canines upper canines not sharpened against the lower premolar and the enamel is thickero Flat face large brow ridge associated with hominins who date to later than 2 mya Early HomininOrrorin tugenensis discovered in 2001 by KenyanFrench team is also similar to both chimps eg incisors canines one premolar and humans eg small maloras thick enamel thigh bones At the Beginning Orrorin Kenya Africa6 million years oldMix of woodland and savannahHominin o Femur suggests bipedalism
More Less

Related notes for BIOLOGY 1M03

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.