Animal Algorithms by Eric Cassell

Author:Eric Cassell
Language: eng
Format: mobi, epub
Publisher: Discovery Institute Press
Published: 2021-09-28T16:00:00+00:00

6. MORE EVOLUTIONARY CONUNDRUMS

What lies at the heart of every living thing is not a fire, not warm breath, not a “spark of life.” It is information, words, instructions... If you want to understand life, don’t think about vibrant, throbbing gels and oozes, think about information technology.1

— Richard Dawkins

WE HAVE TOUCHED ON SEVERAL CHALLENGES TO THE IDEA THAT complex programmed animal behaviors (CPBs) in animals could have blindly evolved. But there are other challenges not yet touched upon, and challenges touched upon that call for a more careful analysis. Here we shift from chapters that focus on particular categories of complex programmed behavior (i.e., navigation and migration, social behavior, architecture) to a chapter that takes up a series of general challenges to CPB evolution. The first we turn to was briefly considered earlier—convergence.

A Tangled Tree

DARWIN’S THEORY of evolution offers a picture of a gradually branching tree of life, with differences among forms growing over time. But then we get something called convergence. Convergence is roughly equivalent to the cladistics concept of homoplasy, which is defined as “similarity in the characters found in different species that is due to convergent evolution—not common descent.”2 Douglas Futuyma defines convergent evolution as the “evolution of similar features independently in different evolutionary lineages, usually from different antecedent features or by different developmental pathways.”3

Convergence (and homoplasy) is to be distinguished from homology, which under Darwinian evolution is defined as a common feature or trait in species that share a relatively recent common ancestor. A common example cited for homology is vertebrate forelimbs, which have the same basic design among various species of vertebrates. In this case, the similarity is assumed to be due to common ancestry and, with it, common genetics and common developmental pathways.

On the other hand, animals with “convergent” characteristics are those thought to have evolved the shared characteristics independently, and not from a common ancestor that had the same characteristic or trait. Classic examples of convergent evolution are Australian marsupials and placental mammals in Northern Hemisphere continents. Placental mammals include anteaters, wolves, cats, moles, and mice. The corresponding Australian marsupials include kangaroos, wallabies, and wombats. A PBS educational page neatly summarizes the conventional wisdom among evolutionary biologists on this point:

Marsupials in Australia and placental mammals in North America provide another example of convergent evolution…. They separated from some common ancestor more than 100 mya, and each lineage continued to evolve independently. Despite this great temporal and geographical separation, marsupials in Australia and placentals in North America have produced varieties of species living in similar habitats with similar ways of life. Their resemblances in overall shape, locomotor mode, and feeding and foraging are superimposed upon different modes of reproduction, the feature that accurately reflects their distinct evolutionary relationships.4

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.