What were four lines of evidence Darwin used to support his argument for evolution?

Answer 1

The classification of lines of evidence into four different types is quite arbitrary. One could as easily distinguish two types, or five, or ten, depending on the criteria used.

For instance: one might distinguish between evidence stemming from research in extant lifeforms on one hand, and from extinct lifeforms on the other. One might distinguish between genetic data and morphological data.

For information on various lines of evidence supporting evolutionary theory, see links below.
1. We have seen species change, and have even caused species to change by our own practices of animal breeding. In recent times we have seen the appearance of such things as antibiotic resistant bacteria and insecticide resistant insects; clearly, they have evolved. They were not always here.

2. In the development of the human embryo (or the embryo of another species) we see that the organism, as it grows from a single celled zygote to a fully developed fetus, goes through what appear to be evolutionary stages. At one point the embryo resembles a fish, having a tail and gills. This is a clear indication that earlier forms from which we evolved are still a part of human genetics.

3. Many species, including humans, have vestigial organs. We have the vermiform appendix, an organ which serves no purpose. More dramatically, whales have very tiny leg bones embedded within their bodies even though they never grow legs. We can find all sorts of residual features left over from earlier stages of evolution.

4. We can trace all sorts of connections, both physiological and biochemical, among different species. The various families and groups which species form, and the similarities within those groups, speak of shared descent and the process of evolution.

Answer 2

Fossil history

Geography

Embryology

and Anatomy