Science of Bias: Becoming Modern Humans

Science of Bias: Becoming Modern Humans

Introduction

• Dr. Alicia P Melis (a.melis@ucl.ac.uk) discusses the science of bias related to the evolution of modern humans.
• Humans have populated and impacted virtually every habitat on the planet.

Human History in Context

• If the Earth's history were represented by a calendar year, humans would only have appeared in the last few minutes.

The Secret to Human Success

• Culture and Cooperation

Cumulative Culture

• Human ecological success relies heavily on the capacity to imitate and transfer knowledge between generations.
• Vertical and horizontal transmission facilitates improvements and incorporates innovations into existing practices and technology.

Historical Examples of Survival

• Lost European explorers in the 19th century
  • Sir John Ross & James Clark Ross (1829-1833): Their expedition was stuck in ice for 2 years, but they survived.
  • Sir John Franklin (1845-1848): All members of the expedition died.
  • Both expeditions were stuck in ice, prompting the question: Why did one survive while the other perished?

Cooperation

• Cooperation involves working together to achieve common goals.
• Humans cooperate in highly flexible ways, even with strangers.

Human Evolution

Common Ancestry

• The last common ancestor of humans and chimpanzees lived around 7 million years ago.
• Humans are primates and, more specifically, great apes.
• Chimpanzees and bonobos are more closely related to humans than to gorillas.

Stages of Hominin Evolution

• Stage 1: Earliest (proto) hominins
• Stage 2: Appearance of Australopithecus spp. and Paranthropus spp.
• Stage 3: Appearance of Homo spp. between 1.8 and 2.5 Ma (Mega-annum, million years ago)
• Stage 4: Appearance of anatomically modern humans around 300 kya (kilo-annum, thousand years ago).

Evolutionary Timeline and Characteristics

• Comparison of chimpanzees, Ardipithecus, Australopithecus, Homo erectus, and modern humans, focusing on:
  • Habitat (Arboreal vs. Terrestrial)
  • Teeth (Molars, Canines)
  • Walking (Quadrupedal vs. Bipedal)
  • Brain Size

• Walking Frequency Comparison (Pontzer, 2012):
  • Chimpanzees: Rare
  • Ardipithecus: Some
  • Australopithecus: Frequent
  • Homo erectus: Frequent
  • Humans: Frequent

Guiding Questions

• Where did humans evolve, and what environmental challenges drove the evolution of Homo spp.?
• When and how did Homo sapiens disperse out of the African continent?
• How did the evolving human lifestyle promote increased cooperation and derived psychological traits?

Climate Change in East Africa

• Tectonic plate movement led to the East African Rift, causing changes in landscape and climate.
• Increased aridity and drastic climate shifts resulted in open habitats (Joordens et al. 2019).

Human Characteristics

• Bipedal walking (with major post-cranial changes)
• Dentition and jaw different from other apes
• Precision grip
• Much larger brains
• Slow development and long juvenile period
• Dependence on elaborate material and symbolic culture, as well as high levels of cooperation.

Advantages of Bipedal Walking

• Improved ability to cool off
• Free hands for carrying objects and offspring
• Easier to stand and see in tall grass

Homo Erectus

• Significant increase in body and brain size (about 60% of current brain size).
• Increased reliance on meat.
• Tool use for extractive foraging and processing animal carcasses (scavenging and hunting).
• Changes in life history, including a prolonged juvenile period.
• Changes in social organization and more cooperation.

Homo Erectus Range

• Homo erectus arrived in Eastern Asia between 1.8 and 1.6 Ma.

Skull Comparison

• Australopithecus afarensis: Skull similar to that of modern chimpanzees.
• Homo erectus: Larger brain, smaller jaw and teeth compared to A. afarensis.
• Homo sapiens: Even larger brain, smaller jaw and teeth compared to Homo erectus.

Increased Cooperation

• Open and more risky foraging niche.
• Challenges in finding food (tubers, seeds) leading to learning from others to extract and obtain food.
• Need for defending carcasses from other predators.
• Hunting activities.
• Cooperative breeding.

Cooperative Breeding in Humans

• Helpless human babies necessitate cooperative child-care.

Evolution of Homo: Interplay of Factors (Kaplan et al. 2000)

• Bipedality leads to freeing of hands for extraction, tool use, and carrying.
• Emergence of African savannahs leads to higher density of mammals and plant storage.
• Feeding niche evolves to be based on high-quality and large package size foods.
• Food sharing & cooperation leads to low mortality rates.
• Investments in embodied capital and lengthened development.
• High adult productivity leads to provisioning.
• Large brains evolve.

Homo Sapiens

• Climate change between 900 kya and 130 kya forced hominins to cope with massive environmental changes.
• Oldest fossils classified as Homo sapiens are from Morocco and Ethiopia (300Ka and 200ka).
• Homo sapiens possessed more sophisticated technology and social behavior than contemporaries in Europe and Asia.
• Control of fire achieved approximately 400kya (recent 2022 paper suggests cooking 700kya).

Migration Patterns

• Major migration out of Africa around 60Ka and possibly another previous migration around 120Ka.

Interactions with Other Hominins

• Neanderthals lived in Europe and Western Asia between 400 kya and 40 kya.
• Homo sapiens replaced other populations, although there was some gene flow between them.
• Interbreeding occurred between modern humans and other Homo species in Europe and Asia (Neanderthals genes in us).
• By 30Ka Neanderthals had disappeared.

The Hunter-Gatherer Past

• Humans have been hunter-gatherers for most of their time on earth (95%).
• Even before agriculture, humans evolved mechanisms to live in cooperative groups.

Cooperation Skills

• Subsistence challenges pushed forward the evolution of traits to enhance sociality and support interdependent lifestyles.
• Motivational/temperament changes
• Cognitive changes (Tomasello et al., 2012)

Comparison of Cooperation Skills

• Chimpanzees vs. Humans (Tomasello et al., 2012)
  • Sharing the spoils: Chimpanzees exhibit dominance and low tolerance, while humans show higher tolerance and more sharing after collaboration.
  • Coordination: Chimpanzees use a leader-follower strategy, whereas humans have joint goals and plans.
  • Social control: Chimpanzees rely on partner choice, but humans employ third-party punishment and reputation.
  • Altruism: Chimpanzees offer instrumental helping, while humans engage in sharing and informing.

Increased Tolerance in Humans

• Humans exhibit greater tolerance compared to other primates, which facilitates cooperation.

Coordination and Joint Plans

• Humans can coordinate and create joint plans to achieve common goals.

Leader-Follower Strategy

• Studies show that individuals take on roles as leaders or followers in coordinating tasks (Bullinger, Wyman, Melis and Tomasello (2011)).

Group Mindedness

• Population growth and competition between groups.
• Larger groups ("bands" uniting to "tribes" or "societies") with central place foraging.
• Challenges to coordinate/cooperate in larger groups with strangers.
• Large-group coordination: Culture and Group identification
• Modern Humans exhibit range of psychological mechanisms that support in-group cooperation like social norms, conventions, institutions and in-group bias (Tomasello et al., 2012).

Cultural Practices and Group Identification

• Good social-learning skills to deal with complexity of subsistence strategies (i.e. tools, hunting).
• Distinguishing between bad and good collaborators (skilful and trustworthy).
• Markers of Group Identity (e.g. “those that speak like me”, “eat like me”, "prepare food like me”).
• Race-based categorisation didn’t play a role in our ancestral environments prior to long-distance migration (Cosmides et al. 2003).

Cognitive Detection of Coalitions/Alliances (Kurzban et al. 2001)

• Coalition encoding occurs even in the absence of shared appearance.
• Cues to coalitions are amplified by adding arbitrary features like colored T-shirts.
• Encoding race is a reversible byproduct of this cognitive machinery.
• Race, unlike sex and age, is not a meaningful category based on evolutionary history.
• Alliances shift, thus any observable feature can acquire social meaningfulness if correlated with alliances.

Social Preferences in Infants (Kinzler & Spelke)

• Social preferences based on race emerge between 2.5 and 5 years of age (Kinzler & Spelke, 2011).
• Social preferences based on language exist at 10 months (Kinzler et al. 2007).
• At 4-5 years, language trumps race.
• Language, but not race, predicts native group membership and carried greater weight in evolutionary history.
• Predisposition to pay more attention to language than to race in denoting coalition group membership.

In-Group Favoritism in Cooperation

• In-group favouritism is not out-group derogation (Balliet et al. 2014).
• People cooperate more with in-group members than unclassified strangers and outgroup members
• Interdependence increases in-group biases.
• Ingroup love develops earlier than outgroup hate (Buttelman & Boehm, 2014; Fehr et al. 2013)
• Ingroup favoritism benefits the group but deprives, directly or indirectly, the outgroup which can lead to resentment.

Developmental Study on Resource Allocation (Buttelmann & Boehm, 2014)

• Group Induction phase: artificial arbitrary group
• Computer game: allocation of positive and negative resources to in-group, out-group and neutral box.
• Results: Children allocate more positive resources to the in-group and more negative resources to the out-group.

Reference

• Bae, C. J., Douka, K., & Petraglia, M. D. (2017). On the origin of modern humans: Asian perspectives. Science, 358(6368).
• Balliet, D., Wu, J., & De Dreu, C. K. (2014). Ingroup favoritism in cooperation: A meta-analysis. Psychological bulletin, 140(6), 1556.
• Boyd, R., & Silk, J. B. (2014). How humans evolved. WW Norton & Company.
• Cosmides, L., Tooby, J., & Kurzban, R. (2003). Perceptions of race. Trends in cognitive sciences, 7(4), 173-179.
• Tomasello, M., Melis, A.P. Tennie, C., Wyman, E. & Herrmann, E. (2012). Two key steps in the evolution of human cooperation: the mutualism hypothesis. Current Anthropology, 53(6), 673-692.