Natural selection can drive the evolution not just of simple traits like coat color or body size, but also of complex traits like the size and
shape of skeletons.
Different environments—with different predators, food sources, or resource limitations—apply different selective pressures on the shape of animal
Important evolutionary insights can be gained by making comparisons among fossils of different ages and locations; comparisons among living
populations under different selective pressures; and by comparing fossil to living populations.
Careful quantitative analysis of the traits of living populations can tell us about mechanisms of selection, including genetic mechanisms, whereas
quantitative analysis of populations of fossilized specimens can provide a record of change over time and even the pace of specific adaptive changes.
Statistical analysis is essential for gauging confidence in conclusions drawn from population data, which can include natural variation, populations
in transition, and measurement error by the researcher.