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Charles Darwin and Evolution: Genetic Science uproots the Tree of Life

Updated on July 1, 2017
Will Apse profile image

The author is a biologist who worked in conservation, aquatic biology, and woodland management over many years.

Darwin's Original Sketch of the Tree of Life
Darwin's Original Sketch of the Tree of Life

Science as a Test to Destruction.

2009 was the 200th anniversary of the birth of Charles Darwin. So how are his ideas holding up?

Two hundred years is a long time for any scientific idea to survive in one piece. It is the business of science to test ideas to destruction.

Nobel prizes are won by iconoclasts. Reputations- and funding- can be secured by those who offer new ways of seeing the world. Darwin's ideas have been subjected to every test that raw ambition and the desire for truth can design.

Out of this onslaught, doubts have arisen- on the role of natural selection, for example- but it is only recently that a key Darwinian idea has been in danger of collapse. Molecular scientists and the increasing power of gene sequencing techniques are to blame. 'The Tree of Life' is in danger of being uprooted.

Part of the Tree of Life by Haekel. Popular representations like this helped Darwin's idea become accepted.
Part of the Tree of Life by Haekel. Popular representations like this helped Darwin's idea become accepted.

Darwin's Tree of Life

The idea of the Tree of Life was fundamental to Darwin’s thinking and he regularly referred to it in 'The Origin of the Species'.

It was also one of the key ideas which allowed him to win wide acceptance of his ideas of evolution because it appealed to a common sense view of the living world. It seemed obvious to Victorians that there were 'families' of plants and animals. Zebras, after all, were similar to horses, less similar to bears and very different to snakes.

A classification system for animals from Karl Linneas in 1753 had gained wide acceptance among natural historians. Darwin's ideas provided a simple and compelling account of how differences and similarities in the natural world could arise and how families of animals were interrelated.

Karl Linnaeus

Linear Evolution

A central idea in the Tree of Life theory was that evolution occurred in a linear way. One kind of animal gives rise to another kind of animal under the pressure of natural selection. Every animal had only one immediate ancestor but since any particular animal or group of animals could give rise to more than one type of new animal, the tree of life had many branches.

The Conventional View of the Tree of Life

Genetic Transfers between Species

Viruses have been shown to transfer genes and even long sequences of DNA from one species to another in lab-based studies.

Together with hybridiastion- interspecies breeding- this is often called horizontal gene transfer.

Horizontal gene transfer Wiki.

Linear evolution is the result of the slow accumulation of changes that result from random genetic mutations. Horizintal gene transfer can explain large jumps in evolution.

Enter the Tree Fellers

For two hundred years evolutionary biologists have studied the bones and organs of related species to understand the similarities and differences that evolution has wrought. The evidence produced by anatomists is one the main strands of evidence in support of Darwin’s ideas. It seemed possible to follow linear evolution in any branch of the evolutionary Tree of Life by studying anatomical relatedness.

Molecular biologists expected to find similar evidence when they studied plants and animals at the molecular level. If the 'Tree of Life' idea was correct, species shown to be closely related by anatomical studies should also be closely related at the cellular and molecular level.

At first the evidence was all positive. The molecules studied in the 1970’s were RNA- chemicals similar to DNA but smaller and easier to analyze with the techniques and equipment of the day.

These early studies of RNA seemed to support the Tree of Life theory. The more closely species were related on anatomical grounds, the more similar their RNA was.

Then, as new, more powerful techniques of molecular analysis became available and the studies shifted to DNA itself, strange anomalies were found.

In the most primitive life forms such as bacteria it was impossible to demonstrate any kind of linear evolution. The genetic codes of related and unrelated species showed routine mixing together of genetic material- either as a result of virus activity or cross species breeding.

In a major study of primitive organisms, 80% of genes showed evidence of being transferred from other species rather arising through linear evolution.

Instead of confirming a 'Tree of Life', molecular studies suggested a complex and confusing 'Web of Life"- at the bacterial level at least.

A Representation of the Relatedness of Microbes at the Genetic Level

W. Ford Doolittle (2000) "Uprooting the tree of life." Scientific American, 282(2):90-5  The new maps of microbial inter-relatedness are complex. Scientists will soon be producing Webs of Life to describe the higher animals, including humans.
W. Ford Doolittle (2000) "Uprooting the tree of life." Scientific American, 282(2):90-5 The new maps of microbial inter-relatedness are complex. Scientists will soon be producing Webs of Life to describe the higher animals, including humans.

Caught in the Web Of Life

For a long while, evolutionary biologists resisted the importance of these findings. They stuck to the idea that the tree of life was the important thing and the cross contamination of genetic material caused by viruses was trivial, just noise in a bigger picture. Besides, they argued it could only apply to the unimportant microbes not to the animals and plants we are most familiar with.

Now that view is under serious threat. Recently, as more animal species are having their complete genomes sequenced it is obvious that cross species genetic exchanges are common and have had a big impact on evolution.

Not only do viruses transmit pieces of genetic code from one species to another, it seems that hybridisation- the interbreeding of unrelated species has a long and important history.

Theories of non-linear evolution

Is the transfer of Genetic Material Significant for Higher Animals?

Some studies suggest that something like 40% of the genetic material in a human being is the result of viral genetic transfer. If this is verified, it will make the 'Tree of Life' look completely redundant.

It would, however, help to explain sudden and great jumps in evolution that have puzzled scientists for a long while. A new piece of the right DNA entering the right species at the right time- by pure accident- could propel change in a way that the minute changes propelled by random mutation cannot.

Gene transfer in humans

Sea Urchin
Sea Urchin
Chordate- a primitive fish
Chordate- a primitive fish
Sea Squirt. A hybrid of a chordate and a sea urchin? Photo by Nhobgood, wikicommons
Sea Squirt. A hybrid of a chordate and a sea urchin? Photo by Nhobgood, wikicommons

Hybridisation

Hybrids are created when different species interbreed. A mule is a cross between a horse and a donkey, a liger is a cross between a lion and a tiger.

On land, cross-species breeding isn’t so easy. Size differences, habitat difference and behavioural differences all introduce obstacles. A lion would rather eat a gazelle than breed with it. An amorous robin has little chance with a squirrel. In the oceans however, most species release eggs and sperm in huge numbers and they float together in a great reproductive soup.

Michael Syvanen of the University of California recently compared 2000 genes that are common to humans, frogs, sea squirts, sea urchins, fruit flies and nematodes. He was trying to use genetic data to construct an evolutionary tree showing the relationships between the six animals. He failed- in a spectacular way- with sea squirts. Half the genes of a sea squirt come from a chordate (an animal with a primitive backbone) and half come from sea urchins. This is quite a mash up and difficult to explain unless a hybrid of strange parentage came into being many millions of years ago.

Human Hybrids

There is evidence that early modern humans hybridised with our extinct relatives, such as Homo erectus and the Neanderthals. Did drunken nights have unforeseen consequences?

http://dx.doi.org/10.1098/rstb.2008.0021

http://blogs.discovermagazine.com/80beats/2008/08/08/neanderthal-dna-shows-they-rarely-interbred-with-us-very-different-humans/

A Revolution in Evolutionary Theory

These new ideas have even made some scientists say that Darwin’s idea of linear evolution and the 'Tree of Life' have had their day.

Just as Newton’s simple, elegant ideas of the physical universe were superseded by Einstein’s complex but real world theories, so Darwin’s ideas of linear evolution may be superseded by new theories of evolution which will reflect the true complexity of life.

An interesting Biography of Charles Darwin


His family, life and work with great illustrations.

http://hubpages.com/hub/A-celebration-of-Charles-Darwins-200-years

Comments

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    • Don Bobbitt profile image

      Don Bobbitt 

      2 years ago from Ruskin Florida

      Interesting and Damned good article. I loved the information and your presentation.

      DON

    • alison monroe profile image

      Alison Monroe 

      2 years ago

      Cool! Awesome! I never saw this illustration of the "web of life" before. What a delightful tangle.

    • moneycop profile image

      moneycop 

      7 years ago from JABALPUR

      GOOD POST....YET I BELIEVE THAT EVOLUTION OF MAN IS ONLY A BELIEF AND NOT ACTUALLY HAPPENED

    • Trish_M profile image

      Tricia Mason 

      7 years ago from The English Midlands

      Absolutely!!!

    • Will Apse profile imageAUTHOR

      Will Apse 

      7 years ago

      It is a fascinating area. The amazing thing with Darwin is how much he got right when so little was known of the fundamentals of living organisms in his day.

    • Trish_M profile image

      Tricia Mason 

      7 years ago from The English Midlands

      I only just found this :)

      Very interesting indeed!

      I look forward to finding out more about this research.

      The idea of the 'web' of life at bacterial level does not surprise me at all.

      And, really, I am not that surprised that an unexpected hybrid could form as a result of viruses, etc.

      Homo sapiens sapiens interbreeding with Homo sapiens neanderthalensis wouldn't be too surprising ~ they are closely related. Even Homo ergastor or erectus is a fairly close relative.

      Scientific research, by its very nature, is ongoing, so there will always be new information to assimilate.

      This is all part of evolution research and will be shown to be correct or incorrect.

      Darwin is still to be praised and respected for his work ~ and would probably be involved in this very research, if he were alive today.

      Very good! :)

    • SamboRambo profile image

      Samuel E. Richardson 

      7 years ago from Salt Lake City, Utah

      Informative hub. I think evolution is possible, but with a "designer's" tweaks. But I don't understand the workings enough to know if this research debunks that idea. I marked you up a notch, though.

    • magnoliazz profile image

      magnoliazz 

      7 years ago from Wisconsin

      Darwin has had his day! Amen!

      Awesome hub, voted up!

    • Shahid Bukhari profile image

      Shahid Bukhari 

      7 years ago from My Awareness in Being.

      This is how the Secular Concept ... the Godless Concept of Self-Existence ... Evolves...

      Every Theory, is countered by Anti-Thesis ...

      And this leads to a New Theory, based on the Synthesis of the Old, and the New, Idea.

    • profile image

      American Tiger 

      8 years ago

      Aren't "Scientific Facts" those things which can be tested, repeated and verified?

      Cool Hub, Will. I'm eager to see where the genomic research leads, m'self.

      Do you think it will smite the minds of guys like god, if all of our research and verifiable facts ultimately lead to knowledge of an Intelligent Designer?

    • Will Apse profile imageAUTHOR

      Will Apse 

      8 years ago

      I think god should read more.

    • profile image

      god 

      8 years ago

      how can ppl be this dumb? evolution is a scientific fact, and always will be one.

    • livelonger profile image

      Jason Menayan 

      8 years ago from San Francisco

      Fascinating. I had read, also, that viruses account for a tremendous number of lasting mutations to our genome. The "tree of life" was a simplified representation of the very complex set of forces that has led to the diverse biome of the world today. Great hub!

    • nicomp profile image

      nicomp really 

      8 years ago from Ohio, USA

      Homology does not prove morphology.

    • Will Apse profile imageAUTHOR

      Will Apse 

      8 years ago

      Thx Tony. I reckon your bio of Darwin is outstanding so I have returned the link compliment.

    • tonymac04 profile image

      Tony McGregor 

      8 years ago from South Africa

      Brilliant! Thanks. It is a rich and informative Hub. Will link to mine on Darwin.

      Love and peace

      Tony

    • Chef Jeff profile image

      Chef Jeff 

      8 years ago from Universe, Milky Way, Outer Arm, Sol, Earth, Western Hemisphere, North America, Illinois, Chicago.

      One thing some people try to do is say that since Darwin did not get everything perfectly correct the first time, therefore his ideas must be wrong. They see scientific advance as proving their contention that evolution was a hoax.

      What you have pointed out extremely clearly is that science is a process, not an end point. As Paraglider has also pointed out in his many hubs, some folks have the wrong idea about how science self-corrects when new evidence comes along. Unlike ideas fixed in stone, true science changes as the evidence points in new directions. It adapts as new discoveries call for it.

      As we see with the debate on climate change, there are many ideas about how this is occurring, but few serious voices have evidence or new discoveries to debunk the idea that cliamte change is indeed occurring.

      Cheers!

      Chef Jeff

    • Will Apse profile imageAUTHOR

      Will Apse 

      9 years ago

      Thx Amanda,

      As you say it is a giant jigsaw. The sciences exploring living things are making huge steps but in many ways we are still only just setting out.

    • Amanda Severn profile image

      Amanda Severn 

      9 years ago from UK

      Brilliant hub Will. There's so much still to be learned, but little by little, the pieces are coming together like a giant jigsaw puzzle.

    • Will Apse profile imageAUTHOR

      Will Apse 

      9 years ago

      There still evolutionary scientists trying to hold onto the tree of life. But I think you are both right. It is time to move on. I am waitng for J Craig Venter to sequence a few dozen more higher animals (in progress now) to see how that impacts on the debate.

    • Sufidreamer profile image

      Sufidreamer 

      9 years ago from Sparti, Greece

      Great work, Will,

      A very good explanation of current work in the field - Darwin laid down some great ideas, but science must move ever onwards.

    • earnestshub profile image

      earnestshub 

      9 years ago from Melbourne Australia

      A great hub Will Apse, Science must always move on.

    • Will Apse profile imageAUTHOR

      Will Apse 

      9 years ago

      Thx paraglider

      I liked the neatness of the 'tree of life' idea but nothing is ever as tidy as we would like it to be. Its the little surprises that keep us busy...

    • Paraglider profile image

      Dave McClure 

      9 years ago from Kyle, Scotland

      Will - this is an excellent hub. It would indeed be surprising (imposible in fact) if Darwin had postulated the perfect theory. Like any scientific theory, it exists to be falsified and replaced by a greater theory which encompasses its successes but also explains its failures, and makes possible further prediction and investigation. Not knowing of the existence of viruse, he could hardly have incorporated viral transfer into his model.

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