Unit 4- Evolution and Systematic

Altruism

When an individual’s behavior has immediate consequence of reducing its own fitness while increasing the fitness of others; explained in three instances of kin selection, reciprocity, and group selection

2 Paths to Inclusive Fitness/ pass on your genes

Direct fitness and indirect fitness

Direct fitness

The number os offspring an individual produces

Indirect fitness

The number of offspring the individual’s relative produces

Kin Selection

An altruistic allele will increase in frequency if individuals with the allele help close relatives and the benefit to those close relatives exceeds the cost to the individual.

Hamilton’s rule for Kin selection

the coefficient of relatedness ( r ) multiplied by the fitness benefit to the relative receiving altruism (b) must exceed the fitness cost to the individual expressing the trait (c ); rb>c

Common Eusociality Properties in species

1) Reproductive division of labor

2) Cooperative rearing of young

3) Generations overlap

Reciprocal Altruism

The exchanging of altruistic acts where individual A pays some cost to individual B, but the cost is recovered in the future when B helps A; this system is maintained because cheaters are penalized

Prisoner’s Dilemma

A situation in game theory where two individuals acting in their own self-interest do not produce the optimal outcome; cooperation leads to better mutual payoffs than mutual defection.

Trait Group Selection

A concept in evolutionary biology suggesting that groups with cooperative traits may have a survival advantage over less cooperative groups, influencing natural selection.

Within Group Selection

acts on the interest of individual, leads to the selection against cooperators

Between group selection

cooperation favored if groups with cooperators outperform the groups with “selfish individuals”

Sibling- Sibling Conflict

Which offspring receives the most resources will have more energy and higher chances if survival

Parent- Offspring Conflict

Parents benefit when they provide enough resources to their offspring while also conserving resources because offspring benefit by receiving a lot more which can be detrimental to the resources of parents and other siblings

Coevolution

Heritable traits in Species 1 drive changes in heritable traits in Species 2 which in turn feed back to affect heritable traits in Species 1

Mosaic Coevolution

Describes how the interactions between species can vary across different environments or geographic regions leading to a “mosaic” of evolutionary relationships

Antagonistic Coevolution

When adaptations in each species leads to the detriment in the fitness of the other species; leads to Red Queen Model; can be affected by geographic variation

Co-Speciation

When the relationships between species is very tight, the speciation of one species will lead to the speciation of the other species

Maintenance of Mutualism

When two species are tightly associated, cheating in Species A might diminish the fitness of Species B, ultimately diminishing the fitness of species A therefore cheating behavior is punished

Batesian Mimicry

Can be considered antagonistic; palatable species resembles an unpalatable one (palatable species reaps rewards of unpalatable)

Mullerian Mimicry

Can be considered mutualistic where two or more species resemble one another (costs is shared)

Carl Linnaeus in the Evolution of Humans and Primates

Proposed the first one to formally group humans with monkeys in Systema Naturae 1735; coined the terms “Sapiens”

Similarities between humans and primates

• Similar arrangement of body parts

• proportionally large brains

• vision more important than smell

• long life with slow growth

• few offspring with extended parental care

• 99% DNA similarities

• Cultural transmission = teach offspring

• simple tools and hunt in groups

Causes of Bipedal Locomotion

• More energetically efficient

• less surface area exposed to mid-day sun

• more surface area exposed to wind

• frees hands for foraging and carrying

• more efficient breathing while walking and running

Adaptations to allow for walking in bipedal hominins

• Foramen magnum is aligned directly beneath the skull

• Pelvis is shortened and broadened

• femur elongated

• foot is arched for walking and the hallux is aligned with the other toes

Traits of early hominids

• upright locomotion

• diminished canines

• longer legs

• changes to pelvic geometry

Out of Africa hypothesis

Suggests hominids left Africa at least three migrations; H. ergaster arose in Africa; some migrated to Asia and Europe and became H. erectus; H. heidelbergensis arose from ergaster and then migratied to Western Eurasia, from which would arise Neanderthals and Denisovans

Hominid Interactions

• Neanderthals co-existed with humans for 150,000 years

• Possible inbreeding depression for the Neanderthals

• Conflict with humans

• Hybridization with humans

Genomics of Human Evolution

• 1-4% of the genome of humans is Neanderthal

• 20-30% of the whole Neanderthal genome can be found across the human population

• Very little signal of Neanderthal genetic material in African populations

Genetic Variation in Hominids

• Greatest genetic diversity is in Africa

• Founder effect meant less genetic diversity the further humans expanded from

• ~95% of overall genetic variation is explained by within-population variation

Benefits and Disadvantages of Plant domestication

Humans can select for higher nutrition, growth speed and standardization of protocols, however artificial selection can lead to maladaptive traits in the wild, additionally clones are more susceptible to parasites, pathogens, and diseases

Constraints for Human Evolution

• physical constraints to different phenotypes

• lack of existing genetic variation for selection to act upon

• constraints due to ancestry and evolutionary history