Evolution by natural selection

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Overview

Evolution by natural selection (EbNS) is a scientific theory which explains the process of species origins, i.e. how the different species of life on Earth came to be.

It is often referred to as simply "the theory of evolution" or just "evolution", although this is actually a conflation of two different concepts:

  • evolution refers to the idea that the nature of a species can change (or "evolve") over time – a fact which can be directly observed over human timescales, especially in lower life-forms such as bacteria.
  • natural selection refers to the idea that competition for scarce resources inevitably leads to a contest in which those who are more "fit", i.e. those individuals whose particular characteristics make them more likely to win the "competition" for those resources, are more likely to survive and pass any heritable component of that "fitness" on to their descendants. This part of the theory explains why the process tends to lead to species improvements, rather than just being random.

These two processes in combination lead to a typically very slow but nonetheless almost inescapable gradual improvement of the "fitness" of any particular species; over longer timespans (millions of years), it leads to the evolution of entirely new species, including (over really long spans of time) forms that are substantially more complex than the original ancestor species.

Manufactroversy

Although EbNS is overwhelmingly embraced by the scientific community, it is stridently opposed by a number of groups who typically base their objections and fake explanations on a particular interpretation of the Christian mythos. None of their objections to EbNS thus far have held up under scrutiny, but they have nonetheless been able to convince a large segment of the American population (and a smaller segment in some other countries) that EbNS is false – largely through propaganda and other information-control techniques.

The main points creationists raise against EbNS relate to whether gradual improvement is sufficient to account for:

  • the creation of life from inanimate matter (an idea never proposed by Darwin but largely accepted as the best likely explanation)
  • the evolution of complex life-forms, especially animals, from one-celled organisms
  • the evolution of humans from animals (specifically primates)

These objections have been extensively addressed by scientists and soundly trampled, often repeatedly due to the same point being raised after having been thoroughly defeated earlier.

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Predictions

This section is currently for taking notes; to be organized later.

  • Tiktaalik, a genus of extinct sarcopterygian (lobe-finned) fish from approximately 375 million years ago (late Devonian period), satisfies ToE predictions that an intermediate form between fish and land-walking creature should have existed at some time (possibly multiple times).
  • More popularly, the evolutionary evidence says that whales evolved on land and returned to the sea, and therefore there should be a transitional form (a possibility often ridiculed by anti-evolutionists); a form was first discovered in the mid-2000s, and many others were subsequently found in the same area.
  • The theory of human-primate common ancestry had a small snag in that the other 3 primates in the group have 48 chromosomes, while humans only have 46; due to the contraints of genetics, the most likely sequence of events was fusion of two chromosomes. When the chimpanzee(?) genome was sequenced, the match was found (human chromosome #2 has markers which match what would result from the fusion of two particular chimp chromosomes).

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