Diversity- Primates

The Primate lineage (Order)

– a success (~431 spp.)

• A clade; all related: prosimians, monkeys, apes, humans

Primates:

> 65 my old; oldest fossils: N. America!!

• Prosiminans (diverged 1st)

adapted for arboreal life

Hominoids (35 mya split from Old World Monkeys)

apes and the hominids (i.e., humans and their extinct ancestors)

Hominids (~6my)

only Homo sapiens + closely related (all extinct) species

Family Hominidae include humans

Fossils & DNA: humans & great apes related

– Humans did not “evolve from apes”; rather share CA

•LCA human lineage ~5‐8 mya w/ others (much evol. Δ in

10+ my; great apes poor proxies for LCA)

–Oversimplification & incorrect: single lineage leading progressively to H. sapiens

Surviving sister group to H. sapiens

Chimpanzees & Bonobos (99% DNA similarity; gene expression differs)

•Many unique derived traits in Hominid lineage

2 important (but not only) keys to distinguish ape vs. human

• 1. Skull, especially foramen magnum

• also: cranial capacity, dentition (rectangle vs. parabolic

teeth pattern in jaw), prognathism

• Pelvis shape impt., other bones indicative of locomotion

• Bipedalism key adaptation exclusive to Hominids

• Evolved 1st , other adaptations (lg. brain, tool use,

etc.) followed

Sahelanthropus tchadensis “Toumaï ”

–discovered: 2001; dated at 6.5‐7.4 mya

–Cranial capacity: 350 cc

–“Chimp‐sized” brain but flattened face,

prominent brow, small canines

(≈Hominid)

–Oldest known Hominid or near‐

Hominid (may pre‐date split of

lineage)

Orrorin tugenensis

6.1‐5.8 mya

Recognized Hominids include

• Ardipithecus (~2 spp.)

• Australopithecines: 4 ‐ 1 mya

– Gracile Australopithecus (~6)

– Robust Paranthropus (~3)

• Homo (~11) diverged from

Australopithecines by ~2.3

mya

• Evol. trends:

– increase in brain & body

size, tool use &

sophistication

– decrease in size of tooth &

skeletal robustness, sexual

dimorphism

Fossil record: >5 different spp.

coexisted (did they interact?)

Hominids were found only in Africa until…

H. erectus spread

Ardipithecus ramidus “Ardi”

– Discovered 1992; 10+ additional finds

dated at 4.3‐4.5 mya [2009: most

complete early hominid specimen from

1994 unveiled]

– 110 lbs. & 300‐350 cc

– Oldest definite Hominid genus

• Bipedal, but arboreal grasping big

toe

Australopithecus afarensis

“Lucy”

Discovered 1974; dated at 3.2 mya

(4‐2.8 mya (>300 individuals))

• 82 lbs & 380 cc

• Bipedal (pelvis, skull)

• 74 km from “Ardi”

– Lineage to Homo?

A. africanus

“Taung child”

– Discovered 1925; dated at 2.5 mya

(3‐2.3 mya)

– Likely Homo ancestor

– S. Africa: Taung (limestone)

quarry

– 79 lbs. & 420 cc (varies‐ sexual dimorphism)

Fossil evidence of Australopithecines

Mostly E. African Rift Valley & S. Africa; outlier in

•Chad (central Africa; Toumai)

•Laetoli footprints

Laetoli footprints

‐ bipedal tracks of 2 individuals assigned

to A. afarensis (dated to 3.6 mya)

• made in wet volcanic ash, dried and hardened

Robust Australopithecines

separate lineage

may/not have led to Homo

Paranthropus boisei “nutcracker man”

– Discovered 1959; multiple fossils date to

2.1‐1.1 mya

– 100‐150 lbs & 488 cc

– Bipedal

– Huge 1” molars; sagittal crest (jaw

muscles)

P. robustus

- 2.0‐1.5 mya; 36 kg & 502 cc

Genus Homo

human being” or “person”

• ~2.5 mya‐present, many similarities w/ genera mentioned

(no 1 accepted as the direct ancestor)

• Coexisted w/ other Homo species (currently 1‐ unique)

• species status of some debated [Homo rudolfensis, H. ergaster, H.

georgicus, H. antecessor, H. cepranensis, H. rhodesiensis and H. floresiensis]

– *Indicates mosaic evolution (and gradual evol.) of

hominid features* (this includes previous genera)

mosaic evolution

the concept that different parts of an organism evolve at different rates, rather than all traits changing simultaneously

H. naledi

• Mosaic evolution example

• iscovered 2013 in South Africa

  • Fossils: 236,000‐335,000 years old

  • 465‐610 cc, arboreal shoulder, odd heel

  • Homo‐like hand, teeth, face, foot

Homo habilis

“handy man” (may be >1 spp.

fossils 2.3–1.4 mya, oldest (1st) known

member of genus, Africa only

• 93 lbs & 500‐900 cc

• Larger brain, flatter face, jaw & teeth

“human”

• Stone flake tools, scavenger & hunter?

– Fossilized skulls show marks from lg. predatory

animals (killed/scavenged)

H. erectus “upright human”

•1.6‐0.2 mya (*most successful*);

evolved in Africa (H. ergaster to

some), spread to Asia by 1 mya;

–Early (1.8‐1.5) & Late (0.5‐0.3); 55‐60 kg &

850‐1100 cc

•Larger brain, creative tools, furs,

fires (widespread by 500 kya)

•Coexisted w/ H. habilis for ~500k,

Paranthropus too

Homo floresiensis “Hobbit”?

•Discovered 2003 (Indonesia); dated to 18k ya

(9 individuals)

•~400 cc, 3 ½’ tall, 55 lbs

•Pygmy, diseased or different sp.? (enigma)

– 1 Skeletal analysis: groups w/ ancient hominids‐

relict population of H. erectus?

H. heidelbergensis “Heidelberg Human”

•~700‐300k ya; traits intermediate to H. erectus & H. sapiens

• ~1200 cc cranial capacity

•2nd Hominid to leave Africa, 3rd would be H. sapiens

•Fossils: likely ancestor to H. neanderthalensis & possibly H.

sapiens (aka “archaic” H. sapiens)

H. neanderthalensis “Neandertals” (sp./subsp.?)

> 300,000 ‐ ~30,000 ya; Europe & Western Asia fossils

•1200‐1900 cc ‐ changed over 300k yrs (>400 individual fossils)

•Coexisted w/, “replaced” by H. sapiens (possibilities?)

•DNA: limited gene flow w/ H. sapiens; signal in non/African H.

sapiens genomes (1‐4% identical); back‐migrations

•Larger brains vs. H. sapiens; innovator‐ gradual accumulation of

technology (tools), cared for sick, burial rituals

Big Question: what happened to Neanderthals?

Many extinction hypotheses; no fossils after ~30k ya; “last

stand” in Gibraltar? (artifacts as recent as 24k ya)

– Replacement*: extinction due to climate and/or competitive

interactions w/ H. sapiens (known as Cro‐Magnon)

– Interbreeding: absorption into H. sapiens

– Never split: ancestor of some modern H. sapiens

Who/What was a Denisovan?

Extinct & recently discovered‐ anatomy unknown; DNA

from finger bone

• genetically distinct from, but shares a more recent ancestor

w/ Neanderthals;

– Dated @ 50‐30,000 ya; Humans & Neanderthals known to occupy

area at this time

H. sapiens “wise human”

~200k+ ya – present; (archaic to 500k ya)

• 1350‐1450 cc ; large relative brain size

• Genetically homogeneous vs. related living spp.

• Evolutionary implications? 1. 2.

• Fossils & DNA: reveal Δ, ancestry w/other living & extinct

spp. (all species related)

Fossil and DNA evidence indicate: “Out of Africa”

• Modern H. sapiens originated, spread in >1 waves (95‐45k ya)

from Africa

– Oldest fossils; genetic diversity greatest in source location

• Genetics: varying degrees of isolation; popul. expansion ~40k ya

(Late Stone Age); prior to this total popul. quite small (1000’s)

– Can trace ancestry of people today to MRCA (not 1st H. sapiens)

• ‘Mitochondrial Eve’ 200k +/‐ ya Africa

• ‘Y chromosomal Adam’ 60‐90k ya Africa

mtDNA and human migration

All modern mtDNA traces ancestry to Africa, 9 major

descendant groups (haplogroups) today

– By ~120‐80 K ya reached Middle East, later Asia

– By ~50 K ya Indonesia and Australia

– By ~40 K ya reached Europe

– By ~20 K ya reached Americas, spread quickly to S. America

mtDNA and human migration

mtDNA

African origin, spread to Americas by ~15‐20kya

Other possibilities include

oceanic travel, coastal routes

Evolution within H. sapiens

anatomical trends: smaller molars, decreased bone mass,

decreased brow ridges, smaller and less protruding face

Cro‐Magnons (more correctly EMH)

1st early modern humans date to ~35,000 ya

– Markedly more sophisticated tools (bone, antler,

etc.), artwork (cave paintings), musical instruments

Cave paintings in France 16K yo

– Coexisted w/ Neanderthals in Europe

for ~ 10K yrs

Human variation (often correlated to climate)

H. sapiens overall‐ flattened face & more projecting chin

(backward shift of tooth rows*)

– *No clear advantage; back (wisdom) teeth crowded‐often removed

• Noses (job‐effectively warm & moisten air)

– Size of projecting nose correlates with climate to which particular

human population is adapted (cold‐ narrow & tall N. Europe)

• Body types vary: cold 1 vs. warm climates

– 1ears/limbs short (Allen’s rule); bodies

hefty (Bergman’s rule)‐ reduces exposed

surface

• Skin color correlates

to sunlight levels‐ Vit D and folate trade‐off

Development of speech and language

Likely evolved gradually; led to great cultural evolution;

complex speech at least 30K ya (less than 60K ya?)

• Longer pharynx* & enlarged areas of brain‐ Broca’s area &

Wernicke’s area (vs. other species); effect of damaging these

• FOXP2 gene linked to speech in humans; most mammals

have it‐ 2 mutations in humans may be critical for speech

development (but not THE speech gene)

– Humans w/ 1 copy of gene have speech impediments

Neolithic Revolution

~ 10,000 ya humans transitioned from hunter‐gatherer

lifestyle to more agricultural existence

• Fitness advantage‐ # offspring (could have been slight)

• Even with periods of famine due to crop failures

• Agriculture independently arose in 3 major areas ~10K ya

– Rice, wheat, corn (artificial selection)

– Asia, Middle East, Central America

• Elsewhere, local (& introduced)

plants were also cultivated

Cultural evolution vs. Biological Evolution

“Memes” a unit of cultural transmission includes ideas,

rituals, gestures, beliefs, songs, innovations (Dawkins)

– ≈ genes relayed across time & space, among non/relatives, may

change (mutate)

• Tempo of change greater in which?

• Genetic vs. cultural system

Sociobiology

E. O. Wilson, Sociobiology: The New Synthesis (1975)‐ new

field of science; placed humans w/in tree of life (Darwinian)

– Animal behavior shaped by natural selection

– Human behavior determined in part by natural and

sexual selection, but also by cultural forces which have

no equivalent in animal societies

– Altruism and kin selection 1 component

Nature vs. Nurture a false dichotomy

Debated since before Darwin

• Complex relationship b/w genes and environment

– combo of genotype + environment interacting that

produces phenotype, whether at molecular, cellular,

organismal, or species level

Natural fallacy or appeal to nature fallacy

philosophical argument (in error) equating whatever is

natural is “good”

– Draws ethical conclusions from facts of nature

Social Darwinism ‐ an eclectic term

Extended biological concepts (namely ≈“survival of the

fittest”) to social policies/society; largely rejected

– Linked to the following ideologies:

– In times of British colonialism, ranked white Europeans at

top of evolutionary attainment; others subject to conquering

& slavery

– Similarities in arguments used by fascists in Europe and

laissez faire capitalists in America

– Connection b/w Darwinism and Social Darwinism?

– In name only, Darwin rejected it

Eugenics movement

• dates to 1880’s

•Biosocial movement: improve genetic composition of human

population

–Initially, proposals to dis/encourage marriages based on phenotypes

(subjective); well‐meaning, progressive & based on science of the

day

–Positive vs. Negative: frequency of beneficial alleles vs.

harmful

–Concept modified into restrictions on immigration & marriage;

forced sterilizations; genocide

–Movement today seeks to

“voluntarily...improve the innate quality

of humankind”

–New questions/

interest with biotech,

ARTs (may alter genome)