ANTH 160 Lecture. Pre-Human Life History lecture

1) Why the inherent difficulty of studying long-term change using behavioral ecological theory?

[Behavioral Ecology (BE) generally focuses on short-term changes, links variation in ecology to behavioral variation on short-term scale, through direct measurement; with long-term macroevolutionary change, cannot easily measure variation in key ecological factors, effects of history are important but not easily measurable either, also can’t extrapolate so-called “long-term” patterns in BE studies to “long-term” macroevolutionary changes – effects of localized conditions, demographic changes, etc.]

2) What are some immediate obstacles to paleobiological / HEE fusion?

a) phylogenetic heritage + tinkering = evolutionary change, but how to properly understand hominid ancestry if it’s unclear whether fossils truly represent ancestors or dead-ends?

b) limitations of fossil data – few specimens, only hard tissues survive; fossils are samples, fraught with error, makes inference difficult; inferring behavior requires a link of behavior to morphology or some environmental condition

c) phenotypes of hominid ancestors can never be firmly established, nor can costs and benefits of past behaviors or traits]

3) Hominid evolution as a series of adaptive radiations rather than a progressive ladder. no single evolving hominid lineage. 5.1

4) In trying to assess appearance of new traits throughout hominid history, must assess costs and benefits of those traits in terms of reproductive fitness. Need to specify conditions that favor those traits, then use whatever evidence available to see if those conditions were met at relevant time period.

4) Uniqueness of humans – in what ways are humans unique? (are all species unique in some way?)

Why haven’t all species developed culture, language, long lifespans, and large brains?

5) Four aspects of humans: all closely related – how to understand chronology?

a) locomotor behavior (bipedalism)

b) foraging behavior (big and small game hunting, extraction of roots, tubers)

c) social structure (group living, cooperation)

d) life history (high fertility, long lifespan, delayed maturation)

bipedalism – earliest evidence from femur bones – 3-4 M ya, Laetoli footprints 3.7 M ya, Lucy – 2.9 M ya, overall distinguishing feature of hominids

why bipedalism? bipedalism more energetically efficient than chimp quadrupedalism and bipedality 5.2

- one estimate shows that a bipedal hominid could travel up to 11 km for the same level of energy expenditure as a chimp over 4 km. as range size increases, more energetic!

- energetic efficiency allows increased body size, increased range size, decreased cost of reproduction

what conditions fostered this? shift to hot, open terrestrial environments where aboreal food resources are limited and where terrestrial resources are distributed in highly dispersed patches over large areas.

6) chimps good model of early hominids since semi-terrestrial, often live in relatively dry African environments, and of similar body size to some early hominids

a) What do chimps eat? Do they hunt? [most diet fruits, plants, also termites, meat] 5.3

- tool use variable (termite fishing, stone hammers crack open palm oil nuts), chimp “cultures”

b) How do we infer early hominid diet? dental wear patterns, jaw apparatus, carbon

isotope mass spectrometry, associations with cut bones (scavenging or hunting?) -

inference is similar to chimp diet, but greater home range, more meat consumption (high-quality foods),

possibly more tool use, possibly more central - place foraging, larger groups due to rich patches

* social behavior linked to the structure of resource availability!

c) What allowed for exploitation of difficult-to-acquire foods? [change in social behavior, mental abilities, technology?]

7) model of recent human origins? single point of origin (Garden of Eden) or multiregional in-situ evolution? If replacement theory is true ~200kya, what could have given early humans such an adaptive advantage?

- marked change in “cultural” traits from archaic to modern humans - new diverse, regional technologies, appearance of artistic forms - new social structure then subject to selection itself?!