Sunday, February 28, 2010

Fancy a Close Shave?

Occam's Razor

No, this is not a Gillette commercial.

Rather it is a comment on Occam's Razor: first to Wikipedia -

Occam's razor (or Ockham's razor[1]), entia non sunt multiplicanda praeter necessitatem, is the principle that "entities must not be multiplied beyond necessity" and the conclusion thereof, that the simplest explanation or strategy tends to be the best one. The principle is attributed to 14th-century English logician, theologian and Franciscan friar, William of Ockham. Occam's razor may be alternatively phrased as pluralitas non est ponenda sine necessitate ("plurality should not be posited without necessity")[2]. The principle is often expressed in Latin as the lex parsimoniae (translating to the law of parsimony, law of economy or law of succinctness). When competing hypotheses are equal in other respects, the principle recommends selection of the hypothesis that introduces the fewest assumptions and postulates the fewest entities while still sufficiently answering the question. It is in this sense that Occam's razor is usually understood. To quote Isaac Newton, "We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances. Therefore, to the same natural effects we must, so far as possible, assign the same causes."[3]

Clear? I thought not. In layman's terms what it means is that given a choice between a simple and a complex explanation to a problem, always choose the simple one. It's probably correct.

This is fine, as far as it goes. Problem is is doesn't go very far.

Some examples. Why is there always a quantity of lost coins down the back of your settee/couch? Where do chickens roost in the desert? What did pre-historic man use for toilet paper? The list is long. The list is fairly endless.

But, is it correct?

I think not.

Let's take one of my favourite examples. One that has perplexed me since first I learned of it when I was (say) 12 or 13. Cro-Magnon man fascinated me. They were, as far as we can tell, modern humans. They would not be out of place walking down a street in London or New York. Yet for 25 to 30 thousand years they wandered about Europe and apparently achieved nothing. It took about that long to invent a wheel.

If, as we are led to believe, they were essentially us, what were they doing all that time? Back to Occam's razor. Occam would have us believe that the simplest explanation is the best and most accurate. They were just killing time. Fossil evidence says they were goofing around for thousands of years, getting nowhere. And the fossil evidence is always right. Right?


Let's back track a little. Our Cro-Frenchie pals were relative latecomers to Europe. Originally we were all Africans. The DNA tells us so. Out of Africa is all the rage.

According to both genetic and fossil evidence, archaic Homo sapiens evolved to anatomically modern humans solely in Africa, between 200,000 and 100,000 years ago, with members of one branch leaving Africa by 60,000 years ago and over time replacing earlier human populations such as Neanderthals and Homo erectus. According to this theory, around the above time frame, one of the African subpopulations went through a process of speciation, prohibiting gene flow between African and Eurasian Human populations.[citation needed] The recent single origin of modern humans in East Africa is the near-consensus position held within the scientific community.[1]

So, if Wiki says so, it must be so.

What no-one really deals with is the why. If Occam is correct and the simplest explanation is the one the Our of Africa makes sense – doesn't it?

Not really.

If our ancestors wandered out of Africa about 60 000 years ago and got as far as Australia by about 45 000 years ago, what I want to know is not how, but why.

Assuming modern humans are the same as our African ancestors then what is interesting is not whether they wandered about all over but why they would bother. Who, for example, would voluntarily “vacation” on the snowy steppes of Siberia when you could just stay put on the warm, verdant coastal strips of India and Southeast Asia?

No-one deals with this. The DNA and fossil evidence says it is so; therefore, it is so. Full stop. Occam's Razor. I'm not convinced.

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