millions of years of change

continuing through Jerry Coyne’s Why Evolution Is True, and i have another comment. There have been plenty of times I would say something if I were writing a full critique of the book, but those are usually too small or too big for my intents on my blog. But this morning I came across a passage that hits the sweet spot.

Chapter two is about the fossil record, and starts in earnest by noting the ‘big patterns’. He discusses how huge the time frames we’re dealing with are, and quickly gives an overview of the forms of life as they appear in the fossil record. Humans are the new comers, he says, with our lineage branching off from that of other primates about 7 million years ago. If the history of life on earth were a year, he writes, then bacteria would appear the beginning of March, and the first human ancestors would arrive around 6am on the 31st of December (p.28).

So the last common ancestor between humans and other primates that presently share the earth with us was 7 million years ago. That means all the changes that have occurred have been within 7 million years.

The next few sections are fossilized evolution and speciation and transitional forms. He uses several examples to show how the fossils have evolved over time. To do this, they remove a core sample of the seafloor (nearly all of these samples are marine organisms), and then it can be dated from bottom to top, and all the specimens within the sample can be examined, etc. Here are the examples given in the book:

a species of foraminiferan, Globorotalia conoidea. they looked at the number of chambers in the final whorl of the shell. Over the course of 8 million years it changed from an average of 4.8 chambers to 3.3.

a radiolarian, Pseuodcubus vema. The trait examined in this sample was the width of the animals cylindrical base. In a 2 million year period, the mean thoracic width changed from about 90 microns to somewhere around 139 microns.

various lineages of trilobites were examined from a sample that spanned about 3 million years. All of these showed evolutionary change in the number of segments in the last body section +/- 2 or 3 ribs. The point here is that the different lineages changed different amounts, at different rates, and even in different directions (some got more while others got less in the same sections of the sample).

The next and last specific example given is two species of radiolaria, Eucyrtidium calvertense and E. matuyamai, which separated from a common ancestor. This time the time frame examined was 3.5 million years, and the anatomical structure was the width of the fourth segment. The size at the start of the column (the bottom, the oldest layers) was about 93 microns. At the youngest layers, E calvertense is around 80 microns and E matuyamai is about 120 microns. So somewhere there was a split and one got smaller while the other got bigger.

Coyne says there are hundreds of other examples of evolutionary change in fossils, including not only marine specimens but also terrestrial organisms such as rodents and primates. Some of these change fast, others barely change at all, he says. But, clearly, he chose the examples he did for a reason: as evidence of his point; that organisms change over geological time.

Did you notice anything about those examples he gave? 8 million years to change the chambers in a whorl of a shell. 2 million years to change 50 microns in size. 3 million years to change the number of ribs by two or three. 3.5 million years to change an average of 20 microns in size.

Humans are supposed to have evolved from our shared ancestor with other primates 7 million years ago, but in 8 million years of documented change, all we see is 1.5 less chambers in the last whorl of a shell. Sure, he said some organisms evolve faster and others slower, but this seems a bit extreme. What’s more, the changes in the examples he gives are barely noticeable, and always leave the form as it was. These changes are all working with existing genetic information. There is nothing even close to novel genetic code, which is necessary for macroevolutionary changes in body plans and categories of organisms (amphibians, reptiles, birds, mammals, etc.).

It is alleged that reptiles evolved from amphibians over 50 million years. Granted, that’s much more time than any of the examples given, but also consider the massive changes that would need to occur in this time frame. if we’re talking about microns of difference (a micron is one millionth of a meter. Take one millimeter (~0.04 inches), and divide that a thousand times… that’s a micron) in a preexisting phenotype over 2-3 (or 8 ) million years, is it reasonable to expect that the creation of brand new phenotypes (something that has not even been shown possible) along with the drastic changes that must occur to them in 50 million years? Yes, count me as incredibly skeptical.

The evidence presented by Coyne is unconvincing that there has been enough time needed for macroevolution to occur, and also that the types of changes necessary could occur in the way darwinian evolution theorizes.

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