Recording-2025-02-26T23:24:41.896Z

Class Announcements

• No specific reading assigned, but lecture content covers important topics related to human evolution.

• Lecture will be recorded and shared for those who missed it.

• Writing assignment number three is distributed; worth 10 points.

• Recommended reading: Wong’s Scientific American article on human dietary evolution.

  • Article ties together previous discussions and serves as good reinforcement.

• Essay style assignment due by noon during finals week; gives students ample time to complete.

• Encourage students to consult with the teacher or TA regarding questions on the assignment.

• Extra time will be allotted for quizzes.

• Final exam will include written notes, no electronic devices allowed.

• Study guide for the final exam to be provided by Monday.

Final Exam Details

• Cumulative final exam with 45 questions covering all 10 weeks of the course.

• Noted that agriculture and domestication occurred during the Holocene, approximately 12,000 years ago.

• Holocene: Period characterized by environmental warming following the last glacial period.

Hunter-Gatherer Populations

• Small, closely-knit groups; social structure differs greatly from agricultural societies.

• Example of the Ache hunter-gatherers used to show kinship dynamics:

  • High fraction of individuals are closely related (primary kin and spouses).

• Relatively low population density, necessitating distance between groups due to mobile foraging lifestyle.

  • Social structure not parallel to that found in other primate species.

Agricultural Societies vs. Hunter-Gatherers

• Agricultural groups typically have larger, more diverse populations.

• Transition to sedentary lifestyles leads to unprecedented population growth and complexity compared to hunter-gatherers.

  • Archaeological evidence shows higher genetic diversity and population sizes associated with agriculturalist lineages.

• Historical context of population dynamics post-agriculture adoption:

  • Sub-Saharan Africa saw rapid agricultural population growth around 5,000 years ago, while hunter-gatherer groups remained stable in size.

  • European agricultural groups displayed slower growth initially, but overtook hunter-gatherers in population size over time.

Gene-Culture Coevolution

• Adaptations such as lactase enzyme production as a case study of gene-culture interactions.

• Lactase persistence influenced by single MCM6/lactase gene with multiple mutations across different global populations.

• Distribution of lactase persistence alleles linked to pastoralism and geography (e.g., higher rates in Northern Europeans).

• Evidence of lactase persistence in populations dependent on sheep, cattle, or goats for milk.

Lactase Persistence and Its Advantages

• Multiple hypotheses explain benefits of milk consumption in early Holocene populations:

  1. Nutritional Density: Milk is calorie-rich and high in fats.

  2. Pathogen Exposure: Increased population density leads to higher exposure to pathogens, making milk consumption beneficial.

  3. Famine Resistance: Availability of milk mitigates risks of malnutrition during famines.

• Data shows that settlements associated with agriculture see significant increases in lactase persistence over generations.

Historical Context of Lactase Persistence

• Ancient DNA studies show mutations associated with lactase persisted, correlating with agricultural innovations.

• Disparities noted between the introduction of agriculture and the rise of lactase persistence alleles in populations.

• Archaeological findings visualize the spread of agriculture and the corresponding rise in lactase persistence across Europe.

Comparative Studies Across Populations

• Research by Sarah Tishkoff on lactase persistence in Eastern African populations, differentiating between those who can digest lactose versus those who cannot.

• Genetic diversity studies demonstrate a mixture of lactase traits in various groups, highlighting the complex history of human dietary adaptation.

• Identical haplotypes observed in lactase persistence make parallels between ancestral populations and their adaptations noteworthy.