April 2007
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Month April 2007

Point of instantiation

BlueprintSoftware Engineers will be familiar with the idea of instatiation, but for those that aren’t, it’s the representation of an idea, an instance of it – or put another way it’s making something abstract concrete. So for example, a blueprint is instantiated into a building, but also the blueprint itself is an instantiation of the architects ideas.

So that’s all straight forward then? Well no, not always. The trouble is that unless you understand where your point of instantiation is you can easily get yourself in a semantic muddle. Talking at cross purposes, from different frames of reference.

For example, take a couple of recent posts on the on the concept of ancestral species and how to count them. The posts are excellent – well thought out and interesting; and conclude…

…a lot of nonsense is said about this or that taxon being “more evolved” that (sic) another. Most recently we heard that chimps are “more evolved” than humans, in this case because they had more selected gene changes. But often the confusion here is that a species is “more evolved” because there has been more taxonomic change over time. However, no matter what the speciation rates in unit time for a given lineage, it is on average going to be close to the rest of its clade, unless the concestor of that clade is so far back down the evolutionary tree that it includes bacteria, which have a generation time sometimes of hours, and elephants that generate every 40 years or so, in which case the number is largely meaningless.’

The problem the author has with the research that led to the conclusion that ‘chimps are more evolved than humans’ is not, I assume, with the findings themselves (that chimp DNA has been changed more by natural selection than human DNA) but rather with the conclusion, the notion, that chimps are ‘more evolved’.

As discussed elsewhere evolution isn’t about progression towards a platonic ideal, or some absolute notion of better. And I suspect that John is right in his hypothesis that:

“All species at a given time have exactly the same evolutionary duration, and on average, probably the same number of ancestral species, as their nearest relatives.”

But this point can only be extrapolated to mean that no species is ‘more evolved’ than any other if your point of instantiation encompasses the entire evolutionary history of a species – all its evolutionary ancestors. However, if your point of instantiation is different – say only the ancestral species since the concestor (most recent common ancestor) as with the research looking at Chimp and Human DNA then ‘more’ has a different meaning. And different implications.

 

Lyrid meteors return this weekend

Lyrid MeteorsThis weekend sees the annual return of the Lyrid meteor shower – the world’s oldest known meteor shower.

It’s expected to peak on Saturday night (21st April) with 10 to 15 meteors per hour – and for those in the UK it looks like it will be a clear night. Which is nice.

Better is contextual not absolute

DNANew Scientist has a report that evolutionary biologists from the University of Michigan have found evidence that chimps are ‘more’ evolved than humans.

It appears that, since we split from our common ancestor around 6 million years ago, chimpanzee DNA has been changed more by natural selection than human DNA.

Evolutionary geneticist Jianzhi Zhang and colleagues at the University of Michigan in Ann Arbor, US, compared DNA sequences for 13,888 genes shared by human, chimp and rhesus macaques.

For each DNA letter at which the human or chimp genes differ from our shared ancestral form – inferred from the corresponding gene in macaques – researchers noted whether the change led to an altered protein. Genes that have been transformed by natural selection show an unusually high proportion of mutations leading to altered proteins.

Zhang’s team found that 233 chimp genes, compared with only 154 human ones, have been changed by selection since chimps and humans split from their common ancestor about 6 million years ago.

Many people probably find these results surprising. Indeed, I suspect many people will simply find it unbelievable or even offensive. But even leaving those people aside, I suspect that most people will be surprised because they see evolution as a progression towards some platonic ideal, some absolute notion of better.

The belief that evolution is a march towards an objective end point is probably due to a mixture of a few things including our own egos i.e. “we’re the best, most evolved, most successful species and everything else is evolving towards being like us, right?” That’s why sci-fi, set in the future, show everyday animals having evolved into furry humans. But the concept is also reinforced by diagrams of the evolutionary tree – which places mammals (and especially humans) at the top of the tree and invertebrates at the bottom.

The trouble is that while the relationship between species can helpfully be represented as branches; the notion of progression from ‘bad’ to ‘good’ from ‘less evolved’ to ‘more evolved’ is also inferred from such diagrams and this is misleading. Sorry, I mean untrue. Humans aren’t better evolved than other species – because better only makes sense from the context of the individual species in a specific niche. Oak trees are best at what they do, where they do it; bacteria species at what they do, and humans at what we do.

So other species, such as chimps, may well be ‘more’ evolved than humans i.e. their DNA has undergone more change; but importantly all species are as equally ‘well’ evolved as each other (and that includes humans) because species are selected by their local environment not against some abstract notion of best.

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