Biological Evolution, Primate Ecology & Human Origins

Science

Not just a body of knowledge but a process. Question-driven, evidence based, approximate understanding of the natural world.

Biological evolution

changes in DNA that result in new species over time.

Natural selection (and its 4 postulates)

Process by which traits become more or less common in a population. One mechanism that causes evolution. 4 postulates: Competition, Variation, Reproduction, Inheritance.

Competition

Resources are limited (Food, shelter, mates). Not everyone can survive and reproduce.

Variation

Individuals are different. Affects ability to compete for limited resources, and ultimately, the ability to survive and reproduce.

Reproduction and Inheritance

Traits are passed from parent to offspring.

Fitness

the relative ability of an organism to survive and transmit its genes to the next generation. Aka reproductive success.

Adaptation

a feature shaped by natural selection.

Homology

trait shared due to common ancestry. Shared through common descent. Common structure, different function.

Homoplasy

traits shared due to convergent evolution. (Analogy: Not shared because of common descent. Common function, but different structure.)

Convergent evolution

independent lineages evolving similar traits (your notes use the term but give no definition).

Vestigial structures

traits that have lost most of their original function; your notes give examples only (tailbones; goosebumps from primates making themselves look bigger).

Transitional fossils

fossils of intermediate forms; your notes give an example only (a predicted animal between fish and frogs was found, showing the origin of tetrapods, 4-limbed animals).

Adaptive radiation

Birds vary in appearance, occupy different niches, differ from island to island (Galapagos finches).

Phenotypic plasticity

the ability of an individual to vary its traits depending on its environment (your notes only say "understand the term").

Behavioral ecology

Evolutionary theory applied to behavior. How does an individual's behavior affect its survival and reproduction.

Tinbergen's 4 questions

4 questions to ask if you want to understand behavior. Adaptive value/function: How does the behavior contribute to fitness? Evolutionary history: What is the evolutionary history of the behavior? Mechanistic basis: What is the mechanistic basis of the behavior, including chemical, anatomical, and physiological mechanisms? Development: How does development of the animal, from zygote to mature individual influence the behavior?

Fruits (frugivory)

Most primates are frugivores, the principal food of many primates.

Leaves (folivory)

Foliage (leaves and stems). Main fallback for frugivorous primates. Preferred food for some (esp colobines).

Insects (insectivory)

Rich in lipids, protein. Easy to digest. Hard to catch.

Seeds (graminivory)

Rich in lipids and protein. Protected by shells and or toxins. Specialization needed to crack nuts.

Gum (gummivory)

Rich in fiber. Requires fermentation in a large colon. Small amounts available (protect wounds on trees). Eaten by small primate species.

Endozoochory

a type of mutualistic seed dispersal where animals eat fruits or seeds and pass them through their digestive systems, excreting or regurgitating the viable seeds far from the parent plant..

Durophagous foods

Thick enameled molars in species that open nuts (durophagous foods).

Fallback foods

always available, eaten when preferred foods are scarce.

Preferred foods

eating in proportion to availability, high quality.

THV

Terrestrial Herbaceous Vegetation.

Insoluble fiber (cellulose)

Basic structural component of plant cell walls. Based solely on glucose molecules. Indigestible by any animal but fermentable by microbial enzymes.

Socioecology

How food shapes social systems.

Philopatry

staying in the group or area where you were born; your notes only use the term (e.g. "females form cohesive kin groups and therefore are philopatric").

Social monogamy / uni-male polygyny / multimale polygyny

one male with one female / one male with several females / several males with several females (your notes use these labels without defining them).

Scramble competition

occurs when increasing the group size results in less food for every individual. Occurs when individuals try to acquire a shared, limited resource (such as food or mates) by getting to it first through speed or efficiency rather than by fighting or directly blocking others

Contest competition

dominants get access to food over subordinates

Provisioning

humans feeding wild animals; (more food → obesity OR more food → bigger populations).

Optimal foraging theory

Organisms should maximize their energy intake (by increasing amount & quality of food consumed) to maximize reproductive success. Organisms should minimize time spent searching for food, food processing, energy directed to digestion, and competition to maximize reproductive success.

Paleoanthropologists

Scientists working with fossils of primates, apes, and humans.

Last Common Ancestor (LCA)

Hypothetical Last Common Ancestor between humans and apes but the fossils have not been found.

Hominin

Creatures more closely related to humans than chimps. (Not to be confused with hominids: african apes.)

Obligate bipedalism

must do it; no other efficient choice (modern humans).

Habitual bipedalism

can do it efficiently and make a habit of it most of the time.

Facultative bipedalism

can do it if they have to (chimps, gorillas, early hominins?).

Foramen magnum

Humans have the foramen magnum at the bottom of their skull rather than the back of their skull because of body position.

Sagittal crests

Large temporalis muscles (chewing muscles).

Zygomatic arches

Huge cheek bones (zygomatic arches where the muscle goes through).

Prognathic

having a face that projects forward; your notes say "less prognathic face" for early Homo.

Postcranial

the skeleton below the skull.

Dimorphism

difference between males and females; your notes use "body size dimorphism" and "canine dimorphism" without defining it.

Gracile vs robust

Robust face and skull with massive teeth for chewing. Gracile australopiths: Females 25-30 kgs, Males 50 kgs, Height 1-1.5 meters, Bipedal.

Macrowear

Macrowear can tell us the age of a fossil.

Dental microwear

complexity measures hardness. For hard, brittle foods there are complex, isotropic texture. For soft, tough foods there's more simple, isotropic texture. Anisotropy measures toughness while complexity measures hardness.

The last supper phenomenon

The microwear only really measures their most recent meals before they die.

Stable isotopes

Different types of plants have different ratios of C3 and C4 isotopes. Captures diets over months/years. C3 plants include trees, bushes, and forbs. C4 plants include tropical grasses.

Trace element analysis (barium/strontium)

Barium concentration in teeth of young individuals reflected nursing on mother's milk. Barium is high right after birth, decreases through infancy and falls to lowest level at weaning.

Phytoliths (plant stones)

Microscopic silica structures found in plant tissue.

Taphonomy

a study of what happens to bone after death.

Oldowan (Mode 1) tools

Mode 1 stone tool technology: carcass butchering, digging sticks.

Acheulian (Mode 2) tools

Mode 2/Acheulian tools in Africa. Biface (hand axe).

Hunting and gathering (H-G)

H-G subsist on wild foods: Gathered plants or hunted animals, including fish. No domesticated plant or animal food.

Amenorrhea

loss of ovulation.

Digestibility

%nutrients digested. Digestion costs: energy expended.

Cooking hypothesis (Wrangham)

cooking is a biological trait. Cooking hypothesis: females would require a protector, both males and females would need to divide labor.

Expensive tissue hypothesis

big brained species pay less for guts: true for primates. Immune system, gut, brains are expensive tissues. If you have a high quality diet you can have a small gut → energy available for brain.

Monopolizable food patches

Cooking creates monopolizable food patches. Regardless of the type of food (meat or plantbased) it takes time to cook. During that time, the food must be defended because it could have easily been stolen.

Microbiome

the community of gut bacteria; your notes say diet type (cooked v raw) can affect its composition.

Obligate terrestriality

living entirely on the ground; your notes list it for H. ergaster/erectus (long legs, less muscled arms, must have slept on the ground).

Human Predatory Pattern (HPP)

Regular exploitation of large animals including percussion-based scavenging for fat-rich contents (bone marrow and brains).

Persistence hunting hypothesis

In the absence of sophisticated stone tools H. erectus could outrun a herbivore who die of overheating before we do.

Meat scrap hypothesis

Meat in any amount is beneficial for meeting micronutrient needs in chimps.

Social hypothesis (why they hunt)

Males seek meat to trade with: Females, for sex; Males, to strengthen social bond.

Ecological risk

Ecological risk is about the probability of failure.

Sexual swelling

Sexual swelling is an indicator of ovulation on female chimps.

Hunter-gatherer / forager

HG or Foragers are people who gain their livelihood fully or predominantly by some combination of gathering, collecting, hunting, fishing, trapping, or scavenging, the resources available.

USO

Underground storage organs (USO), potatoes.

Unstratified hunter-gatherers

Sometimes called egalitarian, simple, small-scale, or just hunter gatherers. Depend on wild food, not agriculture. Relatively simple technology. Central place foraging. Small groups (around 30) organized into bands. Highly mobile. No or little food storage/accumulation. Egalitarianism. Gendered division of labor. Widespread food sharing.

Band (residential or local group)

Residential or local group (camp or band). Median band size 29.5. Usually bands made of 5-10 families.

Ethnolinguistic group

(=society) Median size 895. Unlikely ever to assemble as a group. Shared dialect, art, customs.

Risk buffering institutions

functions to reduce risk when one person/family has a need and another does not.

Xaro exchange (!Kung San)

Gifting of items to each other that creates a network of gift giving. Involved the gifting of nonfood items to defined partners to symbolize underlying relationship of mutual access to alternate residences, resources, and assistance.

Egalitarian complex

No formal leaders (headmen chiefs etc). Status leveling mechanisms: Insulting the meat, taboos against bragging. Gossip and shame for braggards and bullies. Credit for success: hunter whose arrow killed the animals gets credit, widespread exchange.

Direct fitness / inclusive fitness

Direct fitness: your own reproductive success (your notes name it but do not define it). Inclusive fitness can include how many kids your kin has.

Inclusive fitness theory

Natural selection favors traits that maximize inclusive fitness.

Kin selection

Natural selection maximizes not just your direct fitness, but your inclusive fitness. You would help your kin have kids, because it increases your inclusive fitness.

Reciprocity (Trivers)

The immediate cost paid by the altruist is repaid later by the recipient. You scratch my back, I scratch yours (after a delay). Requirement: Cost to donor, Repeated interactions, Opportunities for role reversal.

Biological market theory (trading)

Classes of traders exchange commodities, like goods/services. Commodities are exchanged between individuals that differ in the degree of control over these commodities. Cannot be taken by force. Trading partners are chosen from a range of alternatives. Supply and demand determine the value.

Tolerated theft

(a theoretical framework for food sharing from your reading; your notes name it but do not define it, so check the reading or the Lecture 11 slides).

Cooperative breeders

species in which individuals besides the parents help care for young; your notes cover this under "Food sharing with offspring: cooperative breeders."

Life history theory

Allocation of resources: Growth (early life you are spending most energy on growth), Maintenance (during old age resources are focused here), Reproduction (after puberty resources shift to here).

Pooled energy budget

Human mothers rely on pooled energy provided by others. Minimizes their energetic output.

Provisioning hypothesis vs show-off hypothesis

Show off hypothesis: Men do not eat all the food they produce. Do not provide benefit to their families. Hunt to show off their prowess for social prestige.

Apis mellifera

abundant and ~ubiquitous in Africa. Habitat: forest to desert.

Honey

high-quality and abundant. 3 kg per wild Apis hive. 80% sugar (> 300 kcal / 100 g wet weight). Includes larvae. Good source of vitamins (B's, C).

Fluid-dip

(get access to liquid honey).

Smoke

reduces bees' sensitivity to olfactory signals including to alarm pheromones. Effect lasts 10-15 minutes.

Greater honeyguide

a clue to the antiquity of humans successfully exploiting honey. Can lead humans > 1 km. Calls are specialized for (1) guiding (2) announcing arrival at a hive (within ~50m).

Mutualistic relationship (honeyguide and humans)

Humans are taken only to Apis honey, give special "arrival" call, are saved hours of search time. Greater honeyguides wait up to 1.5 h while humans extract honey and benefit from hole enlargement, smoke (quietens bees), and human extraction of comb → eat comb.

Brood parasite

All honeyguides are brood-parasites reared by other species. No apparent opportunity to learn from parents (so guiding is innate).

H1

Honeyguide guiding co-evolved with honey-badgers → Humans take advantage. (Challenged by research on honey-badgers.)

H2

Honeyguide guiding co-evolved with humans or human ancestors. No extant or likely non-hominoid mutualists. Guiding is an innate behavior. Adequate time.

Stratified societies

Societies in which people are hierarchically divided and ranked into social strata, or layers, and do not share equally in basic resources that support income, status, and power.

Stratified hunter-gatherer (sedentary)

Primary food resources: aquatic. Food storage: common. Mobility: settled or semi-settled. Hierarchy: hierarchical (wealth or hereditary). Slavery: present. Competition: publicized.