Tuesday, November 27, 2007


It is interesting that evolutionists quite often use the term "lineage" to refer to a clade. I feel I've seen this in many contexts. Gene families may be called a lineage. A clade of species may also be called a lineage.

What is linear about these groups of biological entities? I think almost nothing. A clade of genes or species contains a common ancestor. A line can be drawn from that ancestor to any of the terminals. However, the decision of which line to draw is arbitrary, unless a single gene or species is all that is of interest in the clade.

Clades are not lineages, they are clades. Clades are branching diagrams without any inherent linearity. I think referring to clades as lineages provides yet another example of how linear thinking is embedded in the way people see the world. "Tree thinking" is a skill central to understanding biology. But to achieve this skill requires people to overcome innumerable difficulties. Some, such as referring to clades as lineages, seem subtle, but nevertheless probably have an effect on our ability to see biology as a collection of branching processes.

No comments: