Tuesday, September 17, 2013

Evolution is Contagious

Viruses have the ability to swap genes with host organisms. Is it possible that viruses are the driving force behind evolution?

Natural selection cannot create new species. It can only change the distribution of traits within a breeding population. This is microevolution.

At best, microevolution can only reduce the number of traits expressed within a species. By species I mean, a group of organisms that can reproduce when the male of the species joins with the female of the species to produce fertile offspring. This is a breeding population.

Some life forms can reproduce asexually by various means, such as sporing and cell division. Normally we think of species and breeding population as being the same thing. However, when it comes to asexual reproduction, this doesn’t apply. Each member of these “species” is a member of their own breeding population. We refer to them as members of the same species in order to properly classify them.

Scientists have proposed mutation as a means of creating new species. Unfortunately this will not work. Here’s why.

Let’s say a mutation creates a creature that belongs to its very own breeding population. Who will it breed with to perpetuate the new species? It cannot breed with its own species because it’s the only one. It cannot breed with its parent’s species because of the newly formed species barrier.

Some species can overcome this problem by self-fertilization. When enough members of the new species are born, regular sexual reproduction can continue. Some animal species produce hundreds of eggs at a time. This can bypass the above problem since the hatched creatures can reproduce among themselves.

What the mutation process can do is increase the genetic diversity of a species.

Unfortunately, the mutation rate of a single species is almost zero. If you rely on this mechanism alone, the genetic diversity around us would never come into existence.

Fortunately, there is a way out. It also explains why we share more genes with other species than would be expected otherwise.

On The Farm

Imagine a pig and chicken farm. A common virus infects the chickens.

Like all viruses, the little bugs swap genes with their hosts. In this case, the viruses obtain the genes that code for feathers.

The viruses then proceed to infect the sperm and egg cells of the pigs.

The pigs show no outward signs of infection and the farmer does nothing.

While in the new host, the virus starts swapping genes between itself and the host organism. The genes swapped are the genes that code for feathers.

Unfortunately, this has rendered the eggs and sperm incompatible with the eggs and sperm of non-infected pigs.

The farmer then breeds the pigs with each other without any problems, since all the sperm and eggs of the pigs have the same genetic alteration and are therefore compatible. The hundreds of piglets produced now have the unique genes. They can breed with each other but not with regular pigs.

This makes them members of their own species.

Genetic Diversity

It probably takes billions of generations for new non-harmful genes to come into existence for a single species. Let’s call this the mutation rate of a species.

But what if you multiply the mutation rate of that species with the mutation rate of all the plants in the world plus all the animals in the world plus all the viruses and bacteria in the world?

The generation of new genes throughout the world should be relatively common. Through the agency of viruses, the new gene slowly spreads throughout the ecosystem, like ink spreading across a pond. The species that can take advantage of these genes will do so with the result that a new trait has come into existence within that species.

This way a species can benefit from genetic mutation without the normal risks associated with it. Some genes have a radical effect on the appearance of plants and animals. This is what causes the Doberman to look so different from a poodle.

A newly acquired gene could cause a new species to take on characteristics that are radically different from its parent species.

Might evolution to work this way?

When pigs fly, I guess. Smile

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