Evolution occurs in response to environmental pressures, but what environmental pressures are there left to operate on man in such a way that he might continue to evolve when we have a cradle to grave nanny state whose duty is not only to protect him, but to find cures for all defects, even those caused by his DNA?

Faced with this question I long ago came to the conclusion that man might be one of the first species to experience what you might call negative evolution – a species in which his actual body became less adapted to his environment, even though, by externalising properties of his body he will actually come to dominate environment more than he does even at the moment.

However, some recent observations have caused me to muse about whether, while the whole species may be likely to physically deterioriate, some parts of it may still be subject to evolutionary pressure. In making these observations I am not thinking of those few remnants of man still dominated by their environment, but in fact those tribes that inhabit the highest spots in the modern environmental ecosystem.

The observations to which I refer are reports that cane toads are evolving faster than thought, over as few as 50 generations. The other is an anecdotal sampling of the student populations at two Brisbane high schools with quite different socio-demographic bases.

Cane toads are apparently becoming stronger and longer-limbed. The evolutionary theory here is that only the fastest toads are at the forefront of the toad invasion, and they tend to be long-limbed. As a result their mates are also long-limbed, and the species evolves as their offspring are more likely to be long-limbed also. This is not to say that all toads have evolved like this. Presumably the more home-bodied toads have stayed much the same, mate with other home-bodies, and produce undistinguished progeny, but in the areas where toads first established themselves.

The point here is that species may evolve into subspecies, and thus may evolve to a point where they become distinct species. Cane toads may be on this trajectory, at least temporarily.

My partner’s daughters are both willowy beauties. Over twelve months ago they moved from a school in a lower-middle class area to one of the two or three best state schools in Brisbane in one of the highest socio-economic catchments. At their old school kids were continually asking them why they were so thin. At their new school, while I’m sure they still stand out, leanness is the order of the day.

We know, at least in Australia, that obesity and low income tend to run together. We attribute this to poor education, and cost pressures, leading to overconsumption of calorie-dense foods, like Macdonald’s. But could it be more complicated than this?

Could part of the reason be that people in higher socio-demographics select mates for intellectual and aesthetic reasons tied to the urge to succeed? As we know again that good looks help us to succeed, are this subset of our species selectively breeding not just more successful offspring, but offspring who are more likely than others to have a biology that favours good looks, of which leanness is an integral part?

Are the obese and over-weight to some extent victims of negative evolution? Something to think of over the leftover plum pudding, especially if you think fat taxes and “Life. Be in it.” campaigns are the answer.