Anthropology Chapter 2 Analyzing Evolution

his rule says that when all else is equal, we should pick the account that demands the fewest assumptions.
Apply to Science: Looking for the simplest explanation is an operating principle that underlies all scientific practice.
It’s always more parsimonious to posit one law of nature then two.
Science always assumes that nature operated under the same rules and exhibted the same patterns as it does in the present.

Natural selection is the gradual, nonrandom process by which biological traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution.

1. The problem of Biogeogrpahy
2. The problem of Homology
3. The problem of Taxonomic Hierarchy
4. The Problem of Vestigial Structures
5. The Origin and Imperfection of Adaptations

Homologous Traits: These are similarities between organisms that are due to shared ancestry, such as milk glands of the people and dolphins or the spinal cords of people and sharks

Similar features appear independently in 2 different lineages. Example Different structure of eyes of squids and octopuses compared to other vertebrates

omologous structures are modified independently in similiar ways in 2 Lineages. For example people and dolphins both have big convoluted brains which evolved out of smaller and simpler brains on the anceestral mammels. The process proceeded separtely in human and dolphins. Their brains are homologous but their size is different between then produced by parallel evolution

Many Organisms have features that serve no purpose in their lives, even though homologous structures are functionally important in other creatures. Example humans can’t more eyes like other animals but have muscles similiar to those that can.
Vestigial Structures: Muscles that are left over from previous evolution such as the human ear muscle.

The fit between organism and environment is imperfect. So much so that it becomes imperfect and the species no longer reproduce itself and disappears. For example the human eye starts wearing out after 40 years

1. Nuclear Energy
2. Particulate Inheritance
3. Sexual Selection

Finding natural difference between the 2 sexes of a species the species exhibits sexual selection. For example the color of the male over the female. The brighter color overtime has attracted the girl and reproduced more.

Species are groups of actually or potentially interbreeding organisms, which are reproductively isolated from other such groups
If the 2 populations cannot interbreed and produce fertile offspring, a reproductive barrier has been established. They then belong to different species.

The demostraction of natural selection to effect change within an evolving population

Cladogenesis: The splitting of a single species into 2

Allopatric speciation or geographic speciation is speciation that occurs when biological populations of the same species become isolated due to geographical changes such as mountain building or social changes such as emigration. The isolated populations then undergo genotypic and/or phenotypic divergence as: (a) they become subjected to different selective pressures, (b) they independently undergo genetic drift, and (c) different mutations arise in the populations' gene pools.[1]