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A Quick Guide to Evolution

SONY DSCby Ramon Casha; photos by Ramon Casha except sheep and chimpanzee photos - see image description.

Background

Prior to around 1995, when I got onto the internet and started chatting across the Atlantic, I had never heard of "creationism", nor did I have the slightest idea that there were people in any significant numbers who actually believe that the universe is around 6,000 years old or that evolution did not take place. Once I started chatting however, I found out that creationism is a very real problem in the United States, and nowadays it's even finding its way to other countries including Malta.

Creationism is the belief that everything in the Bible is not merely true but literal. Based on this, they calculated that the age of the universe is just over 6,000 years old and therefore anything that suggests a longer timescale is false. Similarly, they believe that every species of animal or plant was created exactly as it is, or with very minor variations, and that evolution did not occur. In their efforts to promote their particular beliefs, they try to get it taught in schools in place of real science, with devastating results on the educational levels of thousands of students. These groups are well-funded and expend a lot of money and effort into disseminating misinformation about evolution and science in an effort to discredit them.

ScorpionfishTo its credit, the Catholic Church generally teaches science, including evolution, properly in its schools - but not all students opt for science, so many people might be left without any knowledge about this fundamental phenomenon of life. In this article I will try to explain evolution in a simplified manner which requires no previous knowledge of biology. Needless to say, in order to summarise and simplify, some details will be left out but the principles are all here.

This is how life works.

ChamaeleonWhat evolution is - and is not

Evolution explains how and why life forms change gradually, generation after generation, to form the various life forms we see around us today. Evolution does not provide an explanation as to how life began - it starts off with life already existing. As such, evolution applies whether one believes that a god created life, or whether life arose through entirely natural processes, or arrived from another planet. Evolution also has nothing to do with non-living things, such as how the universe, or our world, was created. Evolution does not say that God does not exist, nor that he does. It says nothing at all about the existence of any gods - it merely does not require the existence of a god for evolution to take place.

The principles of evolution

Crab Spider on a Field MarigoldIf a tall man and a tall woman have children together, the likelihood is that these will grow to be tall themselves. This is the well understood principle of genetic inheritance. Our cells have DNA - half from our mother and half from our father, and this contains all the information needed to produce a person.

If a 180cm tall man and a 180cm tall woman have children together however, it doesn't follow that they will all be 180cm tall. There are variations between individuals. One may be 190cm, the next 175cm. Again, nothing mysterious here.

From time to time, an individual will be born whose differences go beyond the regular small variations. A couple who are both 180cm tall might have a child who just keeps growing, reaching 230cm tall and towering above everyone else. While sometimes this is caused by a disease, it can also be caused by a mutation - something happens to the child's DNA so that it is not a perfect copy of half the father's DNA and half the mother's DNA. In this case, that child's DNA will contain that alteration and it is likely be passed on to that child's own children in turn.

Scottish Black Face Sheep by John Haslam (http://www.flickr.com/photos/foxypar4/474319401/)

Scottish Black Face Sheep by John Haslam (http://www.flickr.com/photos/foxypar4/474319401/)

If we turn our attention to domesticated animals, farmers and breeders intentionally select those offspring with desirable traits and breed them as much as possible. A race horse breeder will try to get the fastest mare and the fastest stallion and mate them together to get very fast foals, then repeat the process in the next generation. A dairy farmer will try to get as many calves as possible out of his best milk cow, because they are likely to also produce large quantities of milk. The rest are quite likely to end up as beef in a butcher shop before they even get a chance to produce their own offspring. Over many, many generations these differences will accumulate, producing many varieties of sheep, cattle, dogs, cats and so on. This process is called artificial selection.

Obviously, in the wild there are no farmers selecting which animals are to be bred and which are to be slaughtered, but there are other forces at play. Consider a herd of gazelles. Thanks to variations between individuals, some will be able to run slightly faster than others, while others will be slightly slower. Every time that the lions attack, the herd runs off, and the fastest will soon be at the front of the herd, furthest from the lions, while the slowest will be at the back. Every time, the chase ends as soon as the slowest animal is brought down. By the time the breeding season has arrived, the slowest 10% of the herd will have been killed without ever having had a chance to pass on their slightly slower traits. This process is called natural selection, or survival of the fittest. Of course speed is not the only factor - acute hearing and eyesight, stamina, fur the same colour as the background, and so on - all translate into a better ability to survive and breed. Nor is it only the prey that is subject to this selection. The predator also needs traits like speed, a good sense of smell, the ability to move silently, claws to bring down prey and so on. Other factors that can make one individual better able to survive than others include, the ability to get food, the ability to find a mate and defend one's offspring, and so on. If a gazelle mutates so that it gets shorter legs, this mutation will be detrimental to it, making it very unlikely that this mutation will make it to the next generation. On the other hand, if one gazelle gets a mutation that gives it more acute hearing, it will be able to hear approaching predators before the others, making it more likely to survive.

Although a mutation takes place in a single individual, evolution takes place across generations. Usually, a single mutation is barely noticeable unless it causes a marked change in appearance, such as an albino. Since natural or artificial selection ensures that detrimental mutations are halted in their tracks while beneficial ones are propagated, over several generations, the beneficial mutations will accumulate.

Common Blue butterfly on Pennyroyal flowersAs long as all the individuals within a species keep on mixing and breeding together, the likelihood is that they will remain one species. From time to time however, groups of the same species will become separated and unable to breed together. This can happen if, say, changing weather patterns open up a normally-impassable passage to a new territory then closes it up again, or if a freak storm blows some flying animals off course onto a new island. When this happens, any mutations or other changes that happen within one group cannot be shared with the other, so - over many generations - the genetic changes will keep accumulating, making the two populations more and more different, until eventually the DNA is so different they can no longer breed together at all, or if they do they produce sterile offspring (mules). Once this happens, they are different species and there is no going back - from then on they will continue to evolve along different paths even if the two populations are brought back together again.

Q & A

So, are we humans still evolving?

Yes, we are. Every living thing continues to evolve until it becomes extinct. However, we humans have taken control over much of our own destiny. When someone is injured they don't just stay there to starve and die - we take care of them and bring them back to health. If someone has a disability which would be fatal in a wild animal, we make whatever adjustments are necessary to help them live and function in our society. These actions sometimes affect the outcome of natural selection to a great degree, but despite our interventions we evolve nonetheless.

Did we evolve from monkeys?

Chimpanzee, photo by patries71 (http://www.flickr.com/photos/patries71/2898403042/)No, and evolution never said we did. On the other hand, we are apes - or to be more precise, we belong to the biological group called the hominids, commonly known as apes, which includes gorillas, chimpanzees, bonobos and orang utans. Hominids in turn are a sub-group of the primates, which also include monkeys, and primates together with other groups form the mammals. All animals that have hair/fur and produce milk are mammals. Mammals along with other groups form the animals, and animals and plants are the two main groups for all life forms. The classification of life into these groups is a complex study, but one can look at the basic characteristics of humans, and compare these with other forms of life to see where humans fit in. We share more characteristics with frogs than with insects (we have skeletons on the insides), but we share even more characteristics with lions than with frogs (we have hair and produce milk), and if you compare a human with a chimpanzee, there are even more similarities - in fact they are our nearest genetic relatives. Humans have common ancestors with all of these, but the closer we are genetically, the more recent was this common ancestor.

Isn't evolution just a theory?

In science, theory is as good as it gets. There is no "higher level" above theory. It takes a lot of testing and cross-checking before an idea gets to be called a theory. Sometimes, when a theory is expected to apply everywhere in the universe, it is referred to as a law. However this does not imply that the theory in question is more well established or has better evidence.

Evolution refers both to a fact and a theory, in much the same way as gravity. We have the phenomenon of gravity, and then we have Newton's Theory of Gravity which is the explanation of that phenomenon. Evolution is a natural phenomenon. It has been observed both in the lab and in the wild. The theory of evolution, as initially put foward by Charles Darwin, is our explanation of exactly how it works. Of course, in the 150 years since Darwin's time, this theory has been refined and improved many times, as new evidence becomes available. However, no evidence has ever been found that contradicts the basic theory. Science has its methods of checking ideas, and these identify and rectify any flaws, rather than dogmatically oppose change. Despite the extremely high regard with which certain people like Darwin, Einstein, Newton and others are held, their work has been improved upon repeatedly.

Is it true there are doubts among scientists about evolution?

In a word, no. While there are a few creationists who also hold science degrees and who reject evolution, these amount to less than 1%, and most are in fields other than biology.

Ok so how did life begin?

We don't know that yet. Two prevailing non-religious hypotheses are that life developed from non-living things using natural methods (abiogenesis), or that life on earth was "seeded" from life in another planet (panspermia). Experiments have shown that it is possible for certain basic building blocks of life can be created using natural processes similar to earth's early environment, however there's a long way to go before it is proved that life can have arisen entirely from natural processes.

How long did it all take?

The entire universe started 13.8 billion years ago. Our planet earth formed 4.5 billion years ago. The earliest forms of life arrived 3.6 billion years ago. Animals arrived just over half a billion years ago. Mammals appeared 200 million years ago. The great apes appeared 20 million years ago, and 200,000 years ago the earliest humans evolved.