Evolution

Summary

The origin story: Evolution

  • Evolution is a process of gradual, inheritable change of features of species with time through multiple generations
  • The main driver of evolution is natural selection
  • The authors of the theory of evolution are Charles Darwin and Alfred Wallace
  • Earth is actually much older than it appears and is approximately 4 billion years old
  • All organisms on Earth have a common ancestor. This ancestor was probably a simple cell without a nucleus
  • There are multiple lines of evidence that prove the reality of evolution: paleontological, geological, genetic, etc.
  • Evolution still happens around us, and will continue to act in course of our history

Earth is teeming with life. There are bacteria – so tiny that we need a microscope to see them. And there are also elephants and whales – creatures significantly bigger than us. There are plants that use the energy of the sun to make their own molecules. And there are also plants that eat insects to survive. Some flowers are eerily similar to bugs and bees and manage to attract insects, so they would pollinate them. There are living things in the air, too: birds and insects that freely fly, bats and flying squirrels that glide from the tree to tree. Each animal, plant, bacterium, fungus has features that seem to make it perfect for the area that it lives in. It seems that some amazing designer has made billions of drawings, made them alive and let them loose to jump, run and fly around.

Surely, humans and worms are very different from each other? They live in different conditions, they are of different size, they eat different food and they look and act differently. But are we really?

Though there are many differences between a worm and a human, there are similarities, too:

  1. Both animals are composed of cells
  2. The cells of both animals have the same features: a nucleus, mitochondria, other organelles. They work in similar fashion, too!
  3. If we zoom in and compare the DNA of the worm and a human, we would see that there are many similarities here, too. Not only is DNA of both creatures composed of the same building blocks, many genes are quite similar, too. The similarities are so evident that scientists use worms as model objects, studying universal biological processes with their help.

How can this be? How can we share genes with such a different creature? The answer is as striking: we are actually all related. We are all a product of gradual changes, inherited from generation to generation, made in course of many centuries. In other words, all of organisms on this planet are a product of evolution.

The theory of evolution was first described by Charles Darwin in the 19th century in his book “The Origin of Species”. Charles Darwin was pursuing a crucial question: how has life come about? What was the origin of it? His travels and his interest in geology has provided him with a lot of evidence that helped him find the answer:

  • The geologists of Darwin’s time have shown that Earth is actually much older than the Bible states;
  • By studying the rocks, geologists discovered multiple layers, one upon the other. They seemed to correspond to different times in course of our planet’s history;
  • People have found strange skeletons and remains inside the rocks. They looked like this:

Or like this:

 

It seemed that these creatures have lived long before humans, and suddenly died for some reason:

  • There were also traces of major catastrophes in the history that the rocks formed – volcanic eruptions, for example
  • Darwin observed the way people bred horses, chicken and dogs. They could select animals that had the features they liked and then mated them together to get children with the traits they needed. This way, whole new breeds were developed very much unlike each other
  • Darwin went around the world on the ship called “The Beagle”. He saw a tremendous variety of animals during his travels. Among other things, he visited Galapagos archipelago. There he has found out that each island has its own species of finch – and each island finch had a beak perfectly adapted to the food available on this particular island

All of these facts has led Darwin to formulate his theory of evolution. The main statements are as follows:

  1. All organisms on Earth are related to each other
  2. All organisms have appeared as a result of small, gradual changes that are inherited from generation to generation
  3. All species are influenced by the environment around them. In a population of related organisms, only those who are best suited to the conditions around them can survive. This process is called natural selection.

There is a co-author of the theory of evolution. His name was Alfred Russell Wallace. He was also a naturalist. He was acquainted with the research of the time. He also worked as a collector, hunting exotic species in far-off areas of the world, so he had a first-hand experience of the amazing diversity of life. He has written a letter to Darwin, stating his own version of the evolutionary theory. As Darwin has published his findings first, and his version was more substantiated, he is considered the main author. But Wallace is considered a contributor, too.

Present research has greatly expanded Darwin’s theory of evolution. We now know a lot of new things:

  • Most organisms on Earth has common genes
  • The DNA, the “hard drive” of our bodies, can undergo small changes in structure called mutations. These mutations can be inherited and are the reasons of the small and big variations seen in organisms
  • Our Earth is indeed very old. According to evidence, it was formed 4,6 billion years ago
  • Our planet has undergone many changes in course of history. The Earth of many million years ago had a different climate, and continents looked different, too
  • Our common ancestor was probably a simple cell that did not even have a nucleus, similar to the present-day bacteria
  • In course of evolution, single independent cells gave rise to multicellular organisms
  • Because of changes in climate and movement of continents, as well as catastrophes such as a fall of asteroids, many animals died, and other organisms took their place

Evidence Of Evolution

There are multiple lines of evidence that prove that evolution is true:

  • The similarities in structure of our genetic code
  • The similarities in the laws that determines how our bodies work
  • The fossil record – the old remains of organisms that used to live far before us
  • The fact that evolution is still going on. Bacteria and viruses are getting adapted to the medicines we use, developing methods to resist them. The insects adapt to pollution, changing the way they look. Many animals use humans to their advantage – such as city birds. The list can go on and on

Problems With Evolutionary Theory

  1. The fossil record is incomplete. The scientists cannot find many “intermediate” forms between different kinds of organisms. The reason for this is that fossilization – a transformation of the remains to stone – is a complete matter of chance. So it is hard to find examples of animals that lived for a short periods of time.
  2. There are many underlying mechanisms of evolution. Present – day evolutionary theory is much more complex that the one Darwin used to write about. It integrates data from many disciplines. And it still does not fully explain why we have arrived to such a complex world.

Evolutionary biology is beyond exciting. There were multiple amazing creatures in the past. The deep history of our world is not just about the dinosaurs. And the most amazing thing that organisms still change and evolve together. And we are evolving along with them, too.

 

Links and further reading:

[1.] https://commons.wikimedia.org/wiki/File:Phacops_rana_fossil_trilobite_(Windom_Shale,_Middle_Devonian;_Penn_Dixie_site,_New_York_State,_USA)_(17178725587).jpg – trilobite image

[2.] https://commons.wikimedia.org/wiki/File:Anning_plesiosaur_1823.jpg – plesiosaurus image