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February 12 is the anniversary of Charles Darwin's birth, and there is some momentum to recognise this as Darwin Day. The idea has merit- the Theory of Evolution generated a revolution in biology and forever changed how we viewed our place in the world.

Darwin wasn't the first to recognise that evolution occurred. The period of canal construction in England at the start of the Industrial Revolution had yielded geological stratas showing gradual changes in the marine animals preserved as fossils. The famous French naturalist Lamark had already proposed a theory of evolution.

Over 60 families of trilobites from the Cambrian to Permian are now known- a detailed record of gradual evolution

Darwin recognised however, that natural selection would lead inevitably to evolution. Wallace also reached the same insight, largely through his familiarity with the diversity of life in the tropics. Darwin however had amassed far more evidence for natural selection prior to this. This drew on investigations in geology, human selection for domestic breeds, research into diverse groups of organisms like barnacles, and of course the evidence collected from his journey on the Beagle.

It was this combination of geology with biology that led to one of his first brilliant insights. This was that geographic gradients of species-diversity, would mimic time-gradients. This would show evolution in action.

The second insight was a very straightforward deduction. If populations show variation in traits and natural selection operated to eliminate adverse traits, then so long as there was an inheritance mechanism, evolution was inevitable. This deduction rested on two presumptions. The first was that the earth was very old (for a time, Lord Kelvin's estimation of the age of the earth was an obstacle on this, until the NZ physicist Rutherford proved Kelvin's estimate to be wrong).

The second presumption was that this inheritance mechanism existed. This was part of Darwin's brilliance. In the mid-19th C, the mechanism of inheritance was completely unknown. It was only Darwin's broad knowledge of nature that allowed this prediction to be confidently made. Genetics has long since vindicated Darwin.

Darwin was also able to recognise that the sexual selection- preferences by mates for certain traits- would also yield evolution. In this case it would create sexually dimorphic forms- males and females differentiated by traits the mate selects for. The classic example is the plumage of the male peacock.

For human evolution, Darwin combined his knowledge of the distribution of the great apes with our similarities in form. This led to the prediction, long before genetics, molecular biology or fossils could corroborate this point, that we would have evolved from a common ancestor to these great apes. The geographical distribution of these apes also pinpointed our origin to Africa. Darwin has since been proven correct.

Finger nails, opposable thumbs and forward-looking eyes link all primates

For modern biologists, Darwin did much to launch biology as a proper science. The transformation was significant- rather than trying to manipulate the data to fit the conception that a creator-god did everything, the data was allowed to speak for itself. We followed the evidence and based conclusion on where that evidence led us. And that has created a grand and rich story of life on this planet, one stretching back nearly 4bn years.