Typology

How to name a species

• Identify the type specimen (the holotype)

• Identify the paratypes (a few other specimens, if you have them)

By centering one specimen around the type, we assume that variation is noise. The names are also static, meaning that they are just points in time. It is impossible to embed the time component of evolution when naming things.

The Statistics of Evolution

Let us first review the three principles of evolution by natural selection.

• The principle of variation

• The principle of heredity

• The principle of differential fitness

A histogram can be used to depict variation in a population.

A mean is an average. Represented by the Greek letter µ.

A variance is calculated by averaging the squares of the distance of each data point from the mean.

$$\sigma^{2}=\frac{\sum(x-\mu)^2}{N}$$

Where $x$ is one measurement, $\mu$ is the mean, and $N$ is the sample size.

Populations with decreased variance are called leptokurtic, and increased variation platykurtic.

Standard deviation is the square root of the average squared deviation from the mean. It preserves the units of the original data.

Statistical significance is a measure of how much measure we have against the null hypothesis.

Population Approach to Variation

• The distribution tells you what is the most common phenotype value of a certain population.

• An individual near the mean for one phenotype may be three standard deviations away for another.

• No individual is an "ideal" for that population/species.

The range of variation for any specific phenotype, of course ranges over time.

*Image modified from: White TD, WoldeGabriel G, Asfaw B, Ambrose S, Beyene Y, Bernor RL, Boisserie JR, Currie B, Gilbert H, Haile-Selassie Y, Hart WK, Hlusko LJ, Howell FC, Kono RT, Louchart A, Lovejoy CO, Renne PR, Saegusa H, Vrba E, Wesselman H, and Suwa G. 2006. Asa Issie, Aramis, and the origin of Australopithecus. Nature 440:883-889.

Some firsts of the Homo Erectus

• First appearance outside of Africa

• First systematic imposition of preconceived form of lithic tools (basically, similar tools found everywhere)

• First basically modern body proporitons

• First systematic hunting (like wolves)

Differences between Neanderthals and Humans

• Short forearms

• Short leg below knee

• Barrel chested

• Short and stocky

Bergmann's Rule states that populations with less massive individuals are found in warm climates near the equator, and populations with larger body sizes are found farther from the equator

Allen's Rule states that the length of arms and legs and other appendages also have an effect on heat lost, meaning that populations in warmer climates tend to have longer limbs.