A Useful Question • What is the difference between valgus angle and bicondylar angle? Week 7: Lecture 7: Hypotheses about the origins and elaboration of our genus

• Introduction to Life History Theory • Several hypotheses related to appearance of H. ergaster • Return to the Mid-Pleiostocene hominin fossil record Transitions Change in cranium, face, teeth, and body shape as as size! Big Question!

• What processes led from a small bodied -like species to a larger bodied, larger brained ergaster, and then eventually to us? • Useful questions sought within the framework of life history theory Introduction to Life History Theory

• How do members of a species allocate energy through life to accomplish: • survival to and through their reproductive period • reproduction, and offspring care (if any) • growth and development • maintenance of organ systems

• Tasks clearly interlinked and involve trade-offs Some Common Life History Parameters • Metabolic requirements • Gestation length • Number of offspring / litter size • Aspects of growth and development • Age at maturity / age at first birth • Inter-birth interval • Duration of reproductive period • Age mortality profiles etc. Life History links to Socio-ecology

• Links between ecology, anatomy, and behaviour: – Niche(s) – Size of home range – Anatomy: body size, brain size, related to locomotion, dentition, gut, and patterns of growth – Diets (quality and quantity) – Social characteristics etc. Several life history parameters characterizing : • long gestation relative to most , but… • usually born singly and very dependent (secondarily altricial) • weaned relatively early • an extended period of dependency on kin • relatively late puberty and even later first reproduction • relatively short inter-birth intervals & relatively high infant and child survival rates • long life spans that extend well beyond reproductive period in women, and most men

Accounting for changes in brain size, body size and body shape

• Several important hypotheses – Heat adaptations including radiator hypothesis – Expensive tissue hypothesis – Assisted birthing, alloparenting and changes in the nature and course of growth and development – Mental mapping – Social group size Hominins Adapting to Environmental Change? • Late Pliocene environments – Cooling – Aridification – Patchier environments – Increased Seasonality • More grazers Heat adaptations • Bipedal posture reduces body surface exposed to solar radiation • on head and shoulders to keep heat out • Greater applicability in accounting for appearance of Radiator Hypothesis Homo

- Related to patterns of blood flow through brain - A. africanus and Homo have pattern that is different than in Stone Tools

• Earliest: Gona, Ethiopia 2.6-2.5 MYA • Percussion flaking • INDUSTRIAL COMPLEX • Cores, Flakes, Manuports

• Who were the first - makers? – A. garhi? ? – Maybe even P. boisei?? Tool Use

• bones and stone tools associated at Olduvai • FLK Zinj site: bordering ancient Olduvai lake – 2500 Oldowan artifacts – 60,000 bones from small mammals to large

• 1970’s: Hunters / home-base concept Hunting or Scavenging? Shipman in 1980s finds … • No evidence for disarticulation of skeletons • Kinds and proportions of bones found • Specimens with both cut marks and carnivore tooth marks – 5/13 cut marks overlay carnivore tooth marks! Tool Use (cont’d)

• Rick Potts: “butchery” sites – Stone tools “cached” at sites around landscape – Like chimps: stone caches for nut-cracking – Temporary processing areas Significance of these data? • Expensive tissue hypothesis and brain evolution • Changes in diet represent continuation of trends in hominin evolution • Early Homo: – Stone tools, butchery sites: more meat in diet, but… – Importance of increasing to access things like underground storage organs Expensive Tissue Hypothesis (continued)

• Constraint on evolution of brain – The brain is energetically expensive! – Selection pressures may act, but only if benefits outweigh costs – Within living species of , EQ associated with dietary quality – This suggests that foraging strategy, diet and brain evolution may be linked Basal Metabolic Rate (BMR) and Body Weight in Mammals Allometric relationship between brain size and body weight Kleibers Law BMR = kW0.75 How does our basal metabolic rate compare with other mammals?

• Humans have similar BMR as other mammals our size • but a higher percentage of energy used to maintain brain • ~ 20 to 25% in adult humans; higher in infants and children • ~ 8 to 10% in adult chimps • ~ 3 to 5% in many other adult mammals The Expensive Tissue Hypothesis (Aiello and Wheeler)

The Expensive Tissue (continued) Mental mapping (Milton)

• Spider monkey (above) • Howler monkey (to right) Sociality, Development, & Brain Evolution

• How to grow a bigger brain when you • Processes that face anatomical & energetic constraints? complement changes in foraging strategies • Advantages of early weaning and alloparenting • Need for changes in patterns of growth

– Insertion of childhood phase in evolution • Intelligent care-givers and increasing survival of infants and children • Increasing group size and neocortex size • Reduced aggression, more cooperation Evidence for changing development? • + encephalopelvic disproportion (Trevathan) • Dental development & eruption patterns – link between M1 eruption, adult brain size, weaning age, sexual maturity across species (Holly Smith) Development of modern human sociality • Improved conditions for individual survival & growth, longer lifespans, reduced inter-birth intervals – higher net reproductive success! • increased cortical control of sexual behaviour • family - divisions of labour • recognition of socially-defined kinship • economic cooperation based on sexual bonds and kinship • primate dominance hierarchy replaced by kinship • broader social groups with economic and territorial basis For Self-Review • What is life history theory? • Describe important life-history parameters that distinguish humans from other apes • Describe the expensive tissue hypothesis • Describe archaeological evidence of early Pleistocene hominin scavenging. How does this relate to hypotheses about ? • How are greater cooperation and allo-parenting hypothesised to influence the net reproductive success of earlier members of our genus?

Return to the Pleistocene hominin fossil record • When does the Pleistocene begin? – I have been reporting the wrong date! Up until 2009 it was 1.806 mya (~1.8 mya). – Now it is defined as 2.588 mya (~2.6 mya) – So our genus (Homo) probably appeared toward the very end of the Pliocene, or early Pleistocene • Earliest representatives? Ledi-Geraru, Ethiopia (2.8 mya) • Hadar, Ethopia, 2.3 mya; Koobi Fora, Kenya, 1.9 mya H. Erectus vs. H. sapiens sapiens Features of “Classic” H. erectus

• Classic from Java and China • Ave cranial capacity ≈ 1000 (range 850-1225 cc) • Large supra-orbital torus / sulcus • Face moderately prognathic • Angled occipital region • Thick cranial bones • Nuchal torus • Greatest breadth of cranium is low Features of Classic H. erectus (continued) • Sagittal keel /parasagittal depression

• Some post-orbital constriction

• Nasal bones project: beginnings of modern nose!

• No chin

• Some with shovel-shaped incisors African H. ergaster (or H. erectus?) • East Lake Turkana: KNM-ER 3733 and (~1.8 mya) • ~850 cc cranial capacity • East Lake Turkana: KNM-ER 3883 • (~1.6 mya) • ~ 800 cc cranial capacity : differences from classic H. erectus • Generally: thinner supra-orbital torus • Less sagittal keeling • Occipital region less angled • Somewhat thinner cranial bones • Smaller average cranial capacity to Homo sapiens

• Middle Pleistocene: ~780,000 - 125,000 ya • Transitional forms in Africa, and Asia • Not H. erectus but not H. sapiens sapiens either • ‘Archaic Homo sapiens’ ??? – includes , , , Homo neanderthalensis, Homo helmei, , and early Homo sapiens? Homo erectus in Europe? • Numerous sites of Acheulian tools – but perhaps made by “archaic” H. sapiens (aka H. heidelbergensis), not H. erectus • Ceprano “Man” - 850,000 yrs old from Gran Dolina - H. antecessor? • Found in northern Spain (as part of the Atapuerca sites), the crania from Gran Dolina date to 780 kya. • The best preserved individual is a juvenile • Estimated cranial capacity ~1000 cc • Broader frontal than H. erectus • Separated brow ridges and more modern looking mid- face of later humans Mid-Pleistocene Homo in Europe

• Gran Dolina, Petralona, Arago, Steinheim, Swanscombe and a mandible from Mauer (others too) • Some argue this grouping represents new species: Homo heidelbergensis Europe – Mauer

• 500,000-400,000 ya • Type specimen for Homo heidlebergensis Same Location – Different Deposit Sierra de Atapuerca, Spain

• ~ 500-350 kya • Sima de los Huesos • 28+ individuals • H. heidlebergensis • “Young” population • Deliberate burial? African Middle Pleistocene Discoveries

• Evidence of divergence from an H. erectus like species early in the Mid-Pleistocene • Probably in either Africa or western Eurasia • Represented by African fossils such as Bodo (600 kya) and Kabwe (600 – 400 kya ?) • (~315 kya) • Omo Kibish 1 and 2 (200 kya) Africa – Kabwe • ~300,000 ya • Broken Hill/Kabwe, Zambia • 1280 cc cranial capacity • Homo rhodesiensis or heidelbergensis • Extremely robust • Large browridges • Broad face • Face relative modern Human Evolution in the African Mid-Pleiostocene But what about the Asia?

• Narmada, India (~600-400 kya)

• Yunxian, China (~580 kya)

• Are they H. heidelbergensis? But what about the Asia? (continued)

• Fossils in China after 300 kya are certainly more advanced than H. erectus. • Important specimens: Jinniushan (~280-200 kya); Dali (~230-180 kya); Xujiayao (~125-100 kya) • Are they H. heidelbergensis? • Are they related to recent Asian populations? What was H. heidelbergensis? • Now something of a “Wastebasket Taxon” • Larger crania than H. erectus but retains some similarities in head shape; faces more derived • European versions have some traits • African versions have some Homo sapiens traits • Asian mid-Pleistocene hominins sometimes included • Some see it as last common ancestor to and Homo sapiens Like H. erectus…

• Cranium long and low… • Receding forehead • Thick skull bones… • Large supraorbital torus… H. Erectus (Northern China) • Large mandibles… • No chin

Petralona (Greece) Unlike H.erectus … • Larger ave. c. cap = 1200 cc • Reduced post-orbital constriction • More rounded occipital Swanscombe region… (England) • Expanded sides of cranium

Steinhem (Germany) H. erectus An end to the muddle?

• It seems increasingly likely there were at least partially distinct lineages.

• If Africans, Europeans hold together as H. heidelbergensis, probably the stem from which both Neanderthals and modern humans arose, but…

• The problem is the East – the Chinese fossils look more advanced than H. erectus but are they H. heidelbergensis? Three Scenarios (at least)

H. antecessor  H. heidelbergensis  H. neanderthalensis  H. sapiens

H. heidelbergensis (Europe)  H. neanderthalensis only

H. heidelbergensis  Europe  H. neanderthalensis  Africa  H. sapiens What about Homo heidelbergensis-like forms in Asia? A new hominin species: H. naledi

• ~235 to 336 kya • Mix of modern and primitive traits • 550 to 680 cc • Deliberate disposal of dead?

VIDEO(2) http://www.bbc.com/earth/story/20160301-is-this-the-earliest-human?ocid=fbert Image from http://news.nationalgeographic.com/2015/09/150910-human-evolution-change/ A new metaphor

“Berger himself thinks the right metaphor for human evolution, instead of a tree branching from a single root, is a braided stream: a river that divides into channels, only to merge again downstream.” The Homo Line

• The ongoing issues with early Homo are: – How much variation can we expect in one species? – How many species of the genus Homo were there? Which were part of our ancestral lineage? The Neandertals

• Who were they? • Where are they found? • Were they cold adapted? • What were their lifestyles like? • Did they coexist with AMHS? • Why and when did they disappear? Neanderthals: When and Where • 130,000 yrs ago: at beginning of last Interglacial • Last stand: 27,000 yrs ago in Zafarraya, Spain • Westernmost: Close to Atlantic: Spain or Portugal • Easternmost: Altai mountains, Siberia • Northernmost: Wales (or Siberia) • Southernmost: Gibraltar or Southern Israel • 275 individuals known from > 70 sites Map (a little outdated) Major Ideas • Neandertals genetically isolated from AMH in W. Asia by Wurmian glaciation, evolved in Europe from H. heidelbergensis • Pre-sapiens – Neandertals archaic group extinct without issue • Evolutionary continuity – Neandertals widespread and contributed substantial DNA to modern Europeans Neanderthal environments

• 130,000 – 70,000 yrs ago: last interglacial – At warmest point: forests expand, hippos in Britain

• 70,000 yrs ago – Last major Ice Age – Polar ice cap engulfs Ireland, ½ of England – Forests recede, replaced by tundra – Arctic fauna descend: giant bears, cave lions, cave hyenas H. heidelbergensis

• Neandertal primitive features: • long low cranial vault BUT occipital torus reduced, brain bigger, rounder profile

• well developed supraorbital torus BUT H. neanderthalensis smaller than… • large face, broad nose, no canine fossa BUT reduced alveolar prognathism • common absence of chin • broad, relatively flat cranial base Side views Distinguishing features

• AMH: • Neandertals • Shape of braincase… • Shape of braincase… • Smaller browridges • Double arched browridges • Lower squarer orbits • High rounded orbits • Lower narrower nose • High wide nose • Hollowed cheeks (canine fossa) • Inflated mid-face • Flatter more angled cheek bones • Cheekbones swept back • Smaller front teeth • Large front teeth • Strong chin • Weak chin Neandertal features (continued.)

• Flatter frontal bone • Shorter bulging occipital bone (occipital bun, suprainiac fossa) • Smaller mastoid process • Large brain (1125-1750 cc range, mean 1410 cc)

• Retromolar gap behind 3rd mandibular molar Neanderthal cranial anatomy (cont’d):

• Taurodont pulp chamber of teeth Neandertal Postcrania

• 50-65 kg & 150-170 cm • large wide rib cage long clavicle wide scapula, large shoulder & elbow joint • hand with strong grip, wide fingertips • wide hips, large hip joint • thickwalled femur, rounded and curved • wide and strong toe bones • low brachial and crural indexes