What are some characteristics of the early Homo diet that may have led to greater brain size and smaller dentition, as well as a smaller gut?
- Use of fire.
- Greater processing - cooking, et cetera.
- Variation in food.
- Importance of shellfish.
Are humans efficient runners? What about heat dissipaters?
Yes - bipedalism and the increased efficiency of energy consumption contribute to our running efficiency.
Yes - we can disperse heat through evaporation. We also have more eccrine glands than apocrine glands, so we have less body odor and more thermoregulation. Also, changes to melanin production and reduction in size of body hair.
What are some distinctive elements of human sexuality?
- With upright posture, female genitalia became more hidden and male genitalia more exposed.
- Females develop breasts.
- No estrus, so males more reliant on behavioral cues from females to indicate sexual receptivity.
- Single births are the rule and are usually assisted.
- Larger brains and changes in pelvis make childbirth more difficult.
- Born at relatively earlier stages of development.
- Greater development outside the womb may provide benefits for adaptation, but only if lengthy postnatal care is guaranteed.
- Preference for polygyny, but monogamy is the predominant marriage pattern.
- Differentiate between cultural ideals and practices, as well as marriage and sexual behavior.
- Division of labor.
Is there any evidence for division of labor in early Homo?
- Evidence is only indirect.
- Homo erectus:
- male chimps hunt. Contemporary hunter/gatherers, men hunt and women gather.
What is Life History Theory?
- The claim that phenotype consists (in part) of demographic traits:
- Age and size at maturity.
- Number and size of offspring.
- Growth and reproductive investment.
- Length of life.
- - connected by constraining relationships, tradeoffs... including those between
- current reproduction and survival.
- current reproduction and future reproduction.
- number, size, and sex of offspring.
Why is LHT important?
The observation that any mutation that alters rate of fertility or mortality could significantly change the population composition and growth rate. Any change at one age changes the same variables at other ages.
What is the r vs. k model?
- R-selected species are those that invest less per offspring on more offspring that develop quickly and reproduce quickly. Shorter lives. (think birds.) "Reproductive competition."
- K-selected species is the complete opposite. (apes.) "Survival competition."
- Species that don't fit this pattern.
- Assumptions are not coherent. Higher k does not always mean lower R. Mortality rates, for example.
- R and K can simply be reduced to changes in mortality at different ages.
What is Charnov's Symmetry approach?
- Indexes that better explain differences among and similarities with taxonomic groups.
- Ratio of offspring size to maternal size.
- Ratio of relative reproductive effort to adult mortality rate.
- Ratio of adult lifespan to age at maturity.
More on Human Life History:
- Slow maturation. Tendency towards neoteny.
- Long life span/slow aging.
- Postmenopausal longevity. Related to selection against senescence and results in slower aging.
- Weaning before independent feeding.
Traits defining childhood:
- Period of age 3 - 7.
- Slow and steady rate of growth, small body size.
- Large brain, fast growing brain.
- Higher resting metabolic rate.
- Immature dentition.
- Weaned from mother but dependent on older people for care and feeding.
- Sensitive period for maturation of fundamental motor patterns.
- Sensitive period for cognitive and language development.
- Sensitive period for physical development, with plasticity to the environment.
- Provides time to practice complex social skills required for effective parenting.
- Adolescent girls gain knowledge of sexuality and reproduction before they become fertile because they appear more sexually mature.
- Adolescent men appear sexually mature later than girls, reducing competition with full-grown men and letting the sexually mature individuals practice their sexual and social roles.
- Allows a woman to aid her offspring and her grandchildren.
- More advantageous for an older woman to invest in her current children than to produce more.
Wood and Collard's criteria for classifying a species in the genus Homo.
- More closely related to H. sapiens than to Australopiths
- Estimated body mass more like H. sapiens than that of Australopiths
- Body proportions more like H. sapiens than Australopiths
- Post-cranial morphology of an obligate biped
- Teeth and jaws more like H. sapiens than Australopiths
- Shows evidence for modern human growth and development
Important firsts after 1.8 mya and before H Sapiens and Neanderthals:
- First hominins outside of Africa
- First appearance of systematic hunting
- First appearance of home bases
- First systematic tool making
- First use of fire
- First indication of extended childhood
What are the stone tool modes:
- 1. Oldowan, chopping tool.
- 2. Acheulian, bifaces.
- 3. Prepared core (Middle Stone Age, Middle Paleolithic, Levallois)
- 4. Blades (upper Paleolithic, Later Stone Age)
- 5. Microlithic (Later Stone Age, Mesolithic)
- NOTE: The sequence is different in Europe and Africa.