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Evolution by natural selection

Robustness of the theory

A minority of religious people dispute the concept of evolution by natural selection. While many of us see a wonderful world that has evolved by natural processes, they assert that some "super natural entity" such as a god or an intelligent designer created the wildlife, and presumably the universe before that.

Some of those people believe that, by undermining some aspect of Charles Darwin's life or work, they can undermine the theory of evolution by natural selection. This is nonsense! At the time of writing, this topic has been subjected to the relentless "scientific process", the process of reverse-engineering the universe, for about 144 years. Charles Darwin brilliantly kick-started the topic, but anything he said or did no longer matters when judging what is true.

There are few scientific assertions (or theories) that have stood the test of time for 144 years. "Evolution by natural selection" is one of them, and it is one of the most robust scientific assertions around. It is here to stay, for the simple reason that it is now a well-validated statement about the history of this planet.

Three questions

Arguably, there are only 3 important questions:

1. How did the universe begin and subsequently develop?
2. How did life begin and subsequently evolve?
3. What is the nature and fate of intelligence and consciousness?

Some people believe they have learned the answers by supernatural means. These are typically religious people. But people who believe in such revelations often contradict one-another. There is no means of resolving these conflicts. Even if there are gods, religions are incapable of informing us reliably of the nature of such gods. They are only able to generate multiple conflicting stories without hope of resolution.

Science is trying to answer these questions. Eventually it will do so. Science is the process of reverse-engineering the universe. It is gradually telling us about the nature of the universe. Then it may tell us how to create new universes.

While science is busy answering these questions, religions place "gods" in the gaps currently unfilled by science. Sometimes, religions falsely try to make the gaps appear bigger than they are, in order to have enough space in the gaps for their particular gods.

1. How did the universe begin and subsequently develop?

I don't know, even though my degree was in Mathematical Physics. Neither does anyone else - yet. This is the wrong web site to seek an answer to this question! Books I enjoyed reading include:

2. How did life begin and subsequently evolve?

We don't know how it began. We don't even know whether it was on Earth or elsewhere.

But once it was here, it evolved by natural selection.

3. What is the nature and fate of intelligence and consciousness?

This is another hard question! But the nature will be tied to the 2nd question. Whatever its nature, it had its origins in evolution by natural selection.

The fate is simple - when you die, it's all over. Intelligence and consciousness are products of the electrochemical activity of the brain. When that stops, so do they. Sorry! I regret it too, for obvious reasons.

Does evolution by natural selection work?

Some people believe that evolution by natural selection is a speculative theory that isn't true in practice.

In fact, if expressed in the right way, evolution by natural selection is simply an inevitable process that belongs more to mathematical physics (or computer science) than to biology and zoology. It will operate everywhere in the universe, rather like an extra law of thermodynamics.

It isn't a matter of whether evolution by natural selection works. It does, and always will. It is a matter of how much of the variety of life on Earth is caused by evolution by natural selection, and how much (if any) by other means. Given enough time, evolution by natural selection will certainly generate a large variety of different life forms once there is a start. But has there been enough time, and is there another competing process that had a bigger effect?

It is futile to deny evolution by natural selection. The only useful question is whether other processes are at least as important. The answer is probably "only chance is as important".

The expression of evolution by natural selection

There are 3 key features of evolution by natural selection:

1. Replication
2. with variation
3. in a hostile environment

"The gene pool is the statistical consequence of replication with variation in a hostile environment". (Pearson, 2003).

Any system with these features will generate evolution by natural selection. Any! Not just life forms. Ideas. Tunes. Patents. Companies. Policies. Ideologies. Cultures. Computer-network configuration algorithms. Memes.

And Religions! Religions combine ideas, policies, ideologies, cultures, and memes. Each generation obtains its view of its religions by transmission (replication) from the previous generation. There are sometimes variations. There is a hostile environment which may crush some variations, and cause others to undergo further change.

On planet Earth, the gene-pool for a species is changed according to these features. So gene-pools evolve by natural selection. Inevitably and relentlessly. Small gene-pools can change fast. Large ones change slower.

What does the species hierarchy mean?

Consider Human Beings, a couple of types of Tit, and the Sally Lightfoot Crab. Here are their full scientific names.

Kingdom

Phylum

Class

Order

Family

Genus

Species

             

Human Being

Animalia Chordata Mammalia Primates Hominidae Homo sapiens
             

Coal Tit

    Aves Passeriformes Paridae Parus ater
             

Long-tailed Tit

        Aegithalidae Aegithalos caudatus
             

Sally Lightfoot Crab (Galapagos Island version)

  Arthropoda Malacostraca Decapoda Grapsidae Grapsus grapsus

The non-evolutionary view is perhaps that this is simply a way of classifying creatures according to common characteristics. By this definition, it could be arbitrary.

The evolutionary view is that this is a story of part of the last billion years of life on Earth. Sometime before the Cambrian Period, perhaps during the the Vendian Period, there was presumably a reproducing population, equivalent to a species, that is the common ancestor of the entire "Animal" kingdom.

That "Animal" species, for various reasons, separated into a number of other species. So it was no longer a species - it was now perhaps what we would call a Genus of lots species. Just one of those species had a "notochord", running along the body, and carrying nerves - "Chordata". Birds and mammals descended from this species, while crabs didn't.

This "Chordata" species eventually itself separated into a number of species, and so "Chordata" became a Genus, pushing the original "Animalia" up yet another level. Now the ancestors of birds and animals became different species. (While "Arthropods" continued their independent way). One species developed milk and hair and special ear-bones, becoming "Mammalia", while the other developed feathers, becoming "Aves". And there were many others besides. (This shows that "Birds and Animals" is not a good name for a web site!)

And so on. What appeared to be species for perhaps many millions of years eventually separated into multiple species, each time adding a new level to the hierarchy. So the hierarchy is (hopefully) a history of common ancestors, not just an arbitrary classification system.

The hierarchy is still somewhat arbitrary. There is no clear definition about how many levels it should have. Sometimes in the literature there will appear a "sub-phylum" or a "tribe". There are a lot of ancestral species in half a billion years!

Page last updated: 8 January, 2010