Evolution under the microscope

Fossils

There are two features about the fossil record that are consistent with evolution.

1. Overall, there is an increase in complexity over time, for example:

2. There are examples of gradual evolution:

These aspects are well known, and is why I had at first presumed the fossil record supported evolution (see About me).

However, to set against these, it should be noted that:

1a. There are some exceptions to the progressive increase in complexity:

1b. New groups appear abruptly, not by progressive evolution of earlier forms:

The widespread evolutionary explanation for new forms appearing abruptly, is that preceding intermediates existed but were not susceptible to fossilisation. However, this is not a satisfactory explanation because there are many fossils of soft-bodied organisms from the Cambrian and before, as explained in the Cambrian explosion.

2. The gradual evolution that can be discerned in the fossil record is limited and can be accounted for entirely in terms of variation and selection from a gene pool present in the initial population.

A recurring theme on this website is that much evolution can and does occur solely though mixing and selecting from existing genes, i.e. without the production of substantially new genetic material. Unfortunately, all too often this level of evolution is extrapolated to try to justify evolution that would require new genes. This unjustified extrapolation arises partly because biologists do not think carefully enough about, or look closely enough at, the different processes involved in evolution (see microevolution and macroevolution). And this also applies to evidence of evolution in the fossil record.

 


Notes

Notes display in the main text when the cursor is on the Note number.

1. For example, see Karl Niklas, Edward Cobb, A Keith Dunker; The number of cell types, information content, and the evolution of complex multicellularity. Acta Soc Bot Pol 83(4):337-347 DOI: 105586/asbp.2014.034

2. Jonathan Antcliffe, Richard Callow and Martin Brasier. Giving the early fossil record of sponges a squeeze, Biological Reviews (2014), Cambridge Philosophical Society, doi: 10.1111/brv.12090

Page created November 2017.