Modelling Divergence, Inter-breeding and Migration: Species Evolution in a Changing World

This paper presents the results of a series of mathematical models of species and subspecies divergences over time. These models have been carried out so that factors like variations in extinction and fossilisation rates, lineage splitting and interbreeding rates, and migration and back-migration rates can be studied. The results imply that: fossils probably lie more frequently on extinct lineages than usually assumed, common ancestors are probably much further back in time than generally accepted, and migrations, as components of evolution, have occurred far more frequently and much earlier in time than is generally thought. To the degree that such models have verisimilitude, the findings have implications for fossil studies attempting to provide data relating to time and place of common ancestry, and for molecular evolutionary studies relying on assessments from fossil investigations in order to calibrate time and place of origin of groups. The models here used are more complex and include a greater number of factors than those used in the past. In particular they suggest that the commonly accepted assessments of the ancestor of humans and chimpanzees at 5 million years ago (Ma) and modern human at 150,000 years ago (Ka) need to be viewed with caution. They therefore confirm suspicions about origins as voiced by a number of molecular evolutionary biologists in recent years. The findings may have implications far more widely in biology for assessing common ancestry of species than just in human evolution. They may further provide better information about the complexity of “characters” and therefore improve their uses in cladistic analyses.