Your Body - The Fish That Evolved. Dr. Keith Harrison

is a good analogy for nature. This ‘gap in the market’ is the commercial ‘vacuum’ everyone is looking for, something they can do which no one else has thought of, where they will have a monopoly with no competitors. They can make a living while expending the minimum of effort. When others start to compete with them, they will usually try to modify their business to become more efficient (sell sandwiches that cost less to make), or provide an improved service (sell drinks as well), or branch out into new areas where they will again have no competition (sell sandwiches at construction sites), or simply try to out-compete the competition. This is Darwin’s struggle for life (in this case commercial life). Businesses therefore evolve in the same way as species evolve.

      In nature, many species of bird feed on flying insects – they are a protein-rich diet – but there are also insects flying at night when birds are sleeping. Nature abhors a vacuum so this gap in the market was exploited by some nocturnal mammals which evolved wings and became bats. They even evolved wings from their front legs, just as the birds had done before them. Bats superficially resemble birds because they live in the same way.

      Businesses that do the same thing will also tend to look like one another, even if they have no direct connection. This is forced upon them by the requirements of their activity. Sandwich providers on opposite sides of the world must share common features: they will use bread and sandwich fillings; they must have a facility where the sandwiches are made; they must have people making sandwiches; they must have transport to enable them to reach the offices where their customers are; they must have baskets or trolleys to carry the sandwiches; and they must handle money. These are constraints imposed upon them by their lifestyle. Nature is no different.

      Animals that exploit the same gaps in the market in different parts of the world (biologists call these gaps ‘niches’) tend to resemble each other. Sea-birds in the southern hemisphere that paddle on the surface of the sea and dive for fish, swimming underwater by flapping their wings (penguins) look like sea-birds in the northern hemisphere that paddle on the surface of the sea and dive for fish, swimming underwater by flapping their wings (auks like the guillemot and razorbill). Mammals that live permanently in the water hunting fish at high speeds (dolphins) look like predatory fish that live the same way, not like other mammals. The extinct reptile ichthyosaurs also looked like dolphins and predatory fish because they shared this lifestyle – even their name means ‘fish lizards’.

      Different animal groups can therefore end up mimicking each other’s bodies because they live in similar ways, even though they are not closely related. Biologists call this ‘convergent evolution’ because different animals have converged on the same body shape independently, rather than inheriting the same shape from a shared ancestor.

      Evolution never sleeps

      Evolution never stops, but nor is it ever heading towards a goal; it is simply a passive response to natural selection, which in turn never stops. Humans are not, as was once thought, the pinnacle of evolution; evolution has no pinnacle, it goes on for ever. We are not even today’s most advanced species. Every species alive has been evolving for the same length of time – since life first appeared on the planet – and all deserve equal consideration as successful survivors.

      There is a tendency to look at body shapes that have existed in the fossil record virtually unchanged for tens of millions of years – for example, ferns, sharks and crocodiles – and see them as primitive forms frozen in time. However, evolution does not just affect the outside of an animal or plant, it also affects the inside, both the organs and how they function. Even the chemistry of all living things is subject to change. Just because a species looks similar on the outside to a related species that lived millions of years ago does not mean that that group has not evolved for millions of years. Any gardener will tell you ferns suffer from very few diseases and are attacked by very few pests, and very few animals eat them. Their chemical defences are extremely efficient. That does not mean the ancient ferns had similar advantages. Ferns may have spent millions of years evolving these defences while their outer form changed very little. Sharks also suffer from few diseases and crocodiles have such an effective healing capability – recovering from severe wounds in very polluted waters with little infection – that medical researchers are now trying to identify the factors in crocodiles’ blood that defend them against bacteria in the hope of discovering a new drug similar to penicillin.

      Nor are species alive today somehow better than species in the past. Each is or was tailor-made for its own environment. Past species were not intermediates on the way to something else. To put this in a context, we can look back to people who lived 10,000 years ago and see they had less knowledge, less technology, less medicine and less comfort than we have today, but, before we describe them as primitive or backward, we should consider what the world will be like for people 10,000 years in the future. They will have lives and facilities incomprehensible to us. Do we want them to look back at us and see us as primitive or backward intermediates whose only purpose was as stepping-stones on a path leading to them? I don’t think so. We do not exist to prepare the way for future generations. We react to, and survive as best we can in, the world of the present. Evolution does the same. Every species is right for its time. Its time may be short or it may be long, but the very fact that it existed at all indicates that at that moment it was a survivor. We should remember it took life 3,500 million years to produce the dodo. This bird was honed by natural selection to fit the environment of Mauritius. It was only when Europeans arrived and changed that environment by introducing European species that the dodo found itself ill equipped, just as we would be if someone released a pride of lions in our local shopping centre (dodos nested on the ground and were probably too vulnerable to the egg-raiding pigs introduced by the sailors).

      Without human interference, the dodo was a survivor, but survivors are not always easy to spot. No species that lived on the planet 400 million years ago still lives on it today, yet if they were all extinct there would be no life today. There are two ways for species to disappear: their representatives may dwindle in number until the last one finally expires – the classic extinction – or the species may evolve into one or more other species, unrecognisable as the same animal or plant as its ancestors. About 4 million years ago, just such a species swung down out of the trees and strode out onto the grasslands of Africa. That species no longer lives – if we passed it in the street it would be instantly recognisable as different to anything we know – but nor is that species extinct. Like so many before, it has survived by shape-shifting down the ages and into today’s world. Now it is time to consider its descendants.