Superheros or super beings: where is evolution taking us?

Natural selection continues apace in nature, but modern medicine is subverting the process in humans, writes DICK AHLSTROM

Birds do it, bees do it, but do we? Evolution through natural selection is alive and well and making changes in all the species on the planet, but where is it taking us?

Scientists can actually watch the process in organisms such as viruses, bacteria or fruit flies.We know evolution is real because we can apply environmental pressures to drive genetic change in these quickly regenerating species.

It is more difficult to watch in “real time” in humans and mammals, since change evolves slowly over many generations. In this case, the fossil record helps, by, for instance, showing us what our earlier human-like ancestors looked like and what changes occurred.

One way or another change arrives, brought either by external environmental factors working directly on our genes or by spontaneous mutation. And most of the change is spontaneous, says Prof James McInerney of the Department of Biology at NUI Maynooth.

A case of mistaken identity

“The vast majority of evolution is neutral, it is not in response to an external influence. It is because the [gene] replication system makes mistakes,” says Prof McInerney, currently a visiting professor at Harvard University in the US.

This may seem like a bad thing but it is just the opposite. “We need to have genetic variety or pathogens will bring us down. We have to be evolvable,” he says.

“Evolvability is good. We could evolve to a position where our replication system doesn’t make mistakes but that is a very bad idea. The ability to be different turns out to be a good idea a lot of the time.”

The parts of our genomes that change the most, however, are the ones that interact with external forces. “How we interact with the environment makes for most of the change,” says Prof McInerney.

A plague on just one of your houses

He cites an extreme example: the waves of Bubonic plague that swept Europe. Some people survived better than others. “The bacterium that was afflicting the population had a different effect on one blood group than another,” he says. Those who survived passed these resistance genes on to subsequent generations.

Sickle-cell disease is another example, says Prof Aoife McLysaght of the Molecular Evolution Lab at the Smurfit Institute of Genetics at Trinity College Dublin.

This red blood cell-related condition causes anaemia in sufferers, but having it confers an advantage, with the person being less affected by malaria, she says.

“Evolution does a cost/benefit analysis. The benefit of protection against malaria outweighed the cost of being anaemic.”

This kind of natural selection is under way all of the time, but do we have any idea where it is taking us? “Human evolution is still going on but it is hard to know where it is heading,” says McLysaght.

Prof Dan Bradley, professor of population genetics at the Smurfit Institute, agrees. “It is hard to predict because we don’t know what the future holds. But we can’t look at the present and assume we will continue on a straight line.”