BIOL 1010 Introduction to Biology: The

Evolution and Diversity of Life. Spring 2011

Sections A & BSteve Thompson: stthompson@valdosta.edu

http://www.bioinfo4u.net1

Sunday, January 30, 2011

Human evolution — where we came from

Starting after the K-T boundary with the “Age of Mammals.” But mammals actually began much earlier, as we’ve seen . . .Remember the Therapsid Cynodonts during the Permian from last time.

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The Cenozoic Era, Tertiary Period (65-1.8 MYA)

Huge adaptive radiation of mammals . . .Including most of the placental mammals, and the lineage leading to human beings, which began about 60 MYA. For example the “Ida” fossil . . .See http://www.revealingthelink.com/.Geological changes triggered huge climate changes, which molded species turnover. 3

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Plate tectonic events created

the present continents.

About 12 MYA India slammed into Asia creating the Himalayas.This produced a massive cooling effect that reduced the size of tropical forests across all of the ‘old world.’

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Cenozoic Era, Quaternary Period (1.8 MYA-now)

The Pleistocene epoch is all but the last 10,000 years of the Quaternary.Several Pleistocene ice ages had huge effects. Up to 30% of the earth’s surface got covered and uncovered several times.Many familiar organisms had evolved, but there were also many that went extinct, e.g. mammoths, mastodons, and saber-toothed cats.Homo sapiens first appeared 200,000 years ago in Africa, and had spread across much of the world by around 10,000 years ago.

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The Paleos and UCMP Websites do a great job of describing the Cenozoic

http://www.palaeos.com/Cenozoic/Cenozoic.htm and http://www.ucmp.berkeley.edu/cenozoic/cenozoic.html.

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Human evolution . . .Humans are Primates – we all share many physical characteristics and lots of DNA.Primates include tarsiers, lorises, bush-babies, lemurs, monkeys, apes, and humans (also an ape).All primates have:

Grasping hands, most with opposable thumbs;Eyes in front of the skull, which provide an overlapping field of sight with excellent depth perception (binocular vision);A large brain size compared to body size;Flat nails instead of claws; and an . . .Unusually versatile (generalist) anatomy.

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For instance . . .

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The complete primate lineage contains . . .

Prosimians - Lorises, tarsiers, bush-babies, lemurs, and aye-ayes (actually a type of lemur);Simians - Old and New World monkeys;Hominoids - All apes (and humans);Lesser apes – gibbons;Great apes – orangutans, gorillas, chimps, and humans;Hominines – only gorillas, chimps, and humans.

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One more time . . .

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And there’s actually two chimp species — the Bonobo, sometimes called the pygmy chimp, and the ‘common’ chimpanzee.

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Here’s how we’re all related:

Major anatomical shifts highlight transitions.11

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Fossils have filled in much of the detail.From left to right the

primate species depicted on the tree

are: a lemur(Lemur catta), an

adapid (Hoanghonius stehlini), a tarsier

(Tarsius bancanus), an omomyid (Shoshonius

cooperi), a proto-monkey (Eosimias

centennicus), a South American monkey

(Saimiri sciureus), an Old World

monkey (Mandrillus sphinx), a great ape

(Gorilla gorilla), and a human

(Homo sapiens).12

Sunday, January 30, 2011

Hominoid locomotionBrachiation – swinging from one arm to the other while the body dangles below.

Gibbons and Orang’s do it this way.Knuckle-walking – chimps and gorillas run rapidly on all fours with weight resting on knuckles.Bipedalism – distinguishes humans.

Adaptations include shorter arms, longer legs, supportive foot bones, fixed big toe, bowl-shaped pelvis, robust lumbar vertebrae, and foramen magnum beneath skull. 13

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Similarities and differencesMany

changes relate to locomotion.

(Chimp on left, human on

right)

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Dietary adaptations

Size and shape of teeth, generalist versus vegetarian versus carnivore;Big sagittal crest size for strong jaw muscles, especially in vegetarians;Size of jaw bone, again biggest in the vegetarians;Prominence of bony ridge over eyes, jaw protrusion, curve of tooth row.

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Molecular evidence concurs.Genes (coding regions) of humans and chimps are 99% identical.The two complete genomes are 96% identical with differences concentrated in noncoding regions.The only characteristic uniquely Homo is bipedal locomotion.Humans are not descended from other groups of modern apes — rather we’re all descended from a common ancestor around 4.5 MYA!Gibbons, orangutans, gorillas, and chimps are not less evolved than humans — that whole ‘primitive’ versus ‘advanced’ concept that I’ve been discussing.

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Pretty much all genes agree . . .

Hasegawa and Kishino, 199017

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Even our chromosomes are nearly the same

Human chromosomes are on the left, chimp on the right.18

Sunday, January 30, 2011

After the chimp genome was complete in 2005, the news hit the

stands fast and hard.For instance see: http://news.nationalgeographic.com/news/2005/08/0831_050831_chimp_genes.html and . . .http://www.genome.gov/15515096.And a nice video: http://www.cs.ucr.edu/~eamonn/DNA/dnaQT.mov helps with the visualization.

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Based on all evidence . . .

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This is the primate tree.

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And just focusing on the Hominoids . . .

We are the chimps most closely related relative. As Desmond Morris would say the “Naked Ape” or as Jared Diamond puts it “The Third Chimpanzee.”

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Hominine evolutionMolecular techniques can’t be used with most fossils — the DNA is almost always totally gone. Therefore, we . . .Must study the physical characteristics of the fossils that we can find. These include . . .Australopithecines – 4 or 5 species, bipedal. These include A. afarensis and africanus from 4-2.5 MYA. Paranthropus – had extremely large teeth, protruding jaws, big sagittal crest, 3-1.5 MYA, was an evolutionary dead end (or was it – Sasquatch?)Homo – beginning 2.5 MYA, tools, larger bodies and brains, all members are considered humans, evidence of culture, the only living species is Homo sapiens.

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Here’s the relationships.

Interestingly, we see an adaptive radiation

followed by a dramatic fall off in

the number of hominine species at several points; e.g. 1.8 MYA up to five species coexisted in Africa, and 200,000

years ago three species coexisted in

Europe.23

Sunday, January 30, 2011

Australopithecus left more than

just bones.The “Laetoli”

footprints date from 3.7 MYA in Tanzania. They leave evidence of Australopiths’

bipedal locomotory mode.

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The Becoming Human Website does a great job!

http://www.becominghuman.org/Their interactive video is spectacular.

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And the PBS Evolution series is great as well.

http://www.pbs.org/wgbh/evolution/library/07/index.html and http://www.pbs.org/wgbh/evolution/humans/index.html.Be sure to check out their videos and external links.

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The path to us . . .Charles Darwin was one of first to speculate that humans originated in Africa. And now we know this happened at least twice — the original hominines that led to all Homo, and the eventual Homo’s that migrated out of Africa to populate all the rest of the world.

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Why did we evolve? Some say . . .Climatic shifts 12 MYA had enormous ecological consequences:

Hominids moved out of the trees and onto new savannas (but check out ‘Ardi’);This prompted selection for bipedalism;Tool use and language may have spurred evolution of a larger brain;The large brain led to culture — knowledge, beliefs, and behaviors transmitted from generation to generation;Farmers began to replace hunter-gatherers.

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And now in the remaining time today, I want to show you part of a

great video on one the earliest known Hominin human ancestors . . .

Even earlier than Australopithecus. It was nicknamed “Ardi” for Ardipethicus, and existed around 4.6 to 3.8 MYA! The really cool thing

about Ardi is it displays an amazing combination of both modern Homo and non-

human Ape characteristics — bipedalism and a grasping big toe, as well as reduced canines!

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The excerpt is from . . .

Discovering Ardi, a two-hour documentary film from the

Discovery Channel, originally shown in October 2009,

starting at Chapter Nine.30

Sunday, January 30, 2011