Tweet
Darwinian evolution is one of those scientific theories that has been proven true so many times, it is as near to law as one can get in the biological sciences. Evolution is a fact, and while that fact can be disbelieved by some who view the natural world through the prism of faith, it cannot be disproven.
But quietly and with little public fanfare, we are beginning to understand that Darwin saw only a segment of the evolutionary machine, and that evolution itself has evolved over time.
JUST suppose that Darwin’s ideas were only a part of the story of evolution. Suppose that a process he never wrote about, and never even imagined, has been controlling the evolution of life throughout most of the Earth’s history. It may sound preposterous, but this is exactly what microbiologist Carl Woese and physicist Nigel Goldenfeld, both at the University of Illinois at Urbana-Champaign, believe. Darwin’s explanation of evolution, they argue, even in its sophisticated modern form, applies only to a recent phase of life on Earth.
Darwin’s model of evolution is rooted in the fact that the genetic makeup of individuals comes through their ancestry–through their inheritance. Environmental factors of all kinds then act upon those genetic combinations, promoting the continuation of some, and deterring others. But here is where Darwin missed the boat. Because inheritance, it turns out, is not the only way organisms can acquire genes. The can, and do, acquire them from other organisms around them, even those of other species. This relatively recent discovery has been termed "horizontal transfer", while Old Darwin’s inherited mechanism is termed "vertical transfer":
At the root of this idea is overwhelming recent evidence for horizontal gene transfer – in which organisms acquire genetic material "horizontally" from other organisms around them, rather than vertically from their parents or ancestors. The donor organisms may not even be the same species. This mechanism is already known to play a huge role in the evolution of microbial genomes, but its consequences have hardly been explored. According to Woese and Goldenfeld, they are profound, and horizontal gene transfer alters the evolutionary process itself. Since micro-organisms represented most of life on Earth for most of the time that life has existed – billions of years, in fact – the most ancient and prevalent form of evolution probably wasn’t Darwinian at all, Woese and Goldenfeld say.
The proof of horizontal gene transfer and its role in evolution may be the greatest discovery in the evolutionary sciences since Darwin himself. For while Darwin was absolutely correct in explaining what he saw (and later work has only cemented his early explanation of how life works), we can now see that the process of evolution itself has changed–or if you like–evolved. As science writer Mark Buchanan puts it, "Early evolution may have proceeded through a series of stages before the Darwinian form emerged."
Buchanan’s recent, short, excellent article on these revolutionary discoveries can be read here, at the journal New Scientist. Highly recommended as one of the most important news stories and scientific discoveries you probably never heard about.
22 Comments
While it certainly seems to true that a “horizontal” mechanism for evolution would have ramifications for development of microbial life, it also seems to true to me that the natural selection of the “vertical” sort would still be the primary or sole mechanism by which non-microscopic life evolved. Chuck’s determination of evolution remains unequivocally the most important work in the history of biology, is my lay belief.
I encourage you to read the entire article–it’s a short and easy read. The new “horizontal” model doesn’t disprove anything in the Darwinian mechanism. Darwin is on rock-solid ground, as always.
Dr. Lynn Margulis has been the major proponent of this concept over the last three decades.
http://www.isepp.org/Pages/San%20Jose%2004-05/MargulisSaganSJ.html
Read her book “The Symbiotic Planet”. The truly major advances in evolution are all examples of symbiogenesis. The theory of Darwinian evolution, while not incorrect, is merely a description of how comparatively minor details are sorted out via competition, after the major developments have occurred via symbiosis.
Long ago I read a science fiction book that has as it’s premise that viruses were the dominant life form on Earth and that when man finally screwed things up so bad, the viruses would ‘take care’ of man.
Wish I could remember the show I saw where it was shown that evolution is an inherent process within existence. In lieu of that, here’s something to ‘chew on’.
Great post, CO. I used to be a biologist long ago…
Really Darwin didn’t “miss” this. In fact, his interest in hybridization demonstrates an incredible curiosity for the mechanism of the change underlying variation across species.
Darwin didn’t have a complete theory of inheritance, and struggled with it for decades. His own theory, Pangenesis, was stillborn, though Darwin never finally renounced it formally.
If your point is that the neo-Darwinian synthesis has not taken account of horizontal gene flow, then I can’t gainsay you (mainly because it’s outside my area of expertise). In any case, Darwin kept his emphasis on variation per se, and stayed agnostic re its sources. Natural selection is still at work whether the genes come from internal mutation (point mutation, errors in codons) or from external gene flow. The point remains, if the change in DNA is helpful, the new DNA or gene tends to be perpetuated. If it is not helpful, the fact it came from another organism is not really germane. The change will not take in the population.
Anyway, a fascinating article you’ve brought us here, and an example that science continues to ask questions and seek answers even in areas already supposedly settled.
interesting .. I wonder if that’s why my lizard is green. ..:)
There’s a quite a bit of symbiotic life in corals and nudibranch species. It’s not a big stretch of the imagination that they could transfer DNA at some point.
Bottom line: An organism can build a new “feature” or steal a new “feature”.
As we know, stealing (by eating perhaps?) is very efficient. Timely, and much less risk and effort.
Building new “features” always struck me as “risky” for a species…
Can’t agree with this:
“after the major developments have occurred via symbiosis”
The major development of a gene is by being built (invented) in one organism. Propogation to multiple species can be by symbiosis or acquisition.
Darwin’s work is important but I’ve never felt it to be the complete answer.
I’ve never been able to fit the sudden and rapid appearance of civilization 5K years ago into a model of evolution.
Just more mysteries to be solved.
Excellent point. I was using Darwin generically–referring to the modern synthesis as a whole, including Mendel, Watson and Crick, etc. In my defense, Darwin also believed in some element of heritability–he simply didn’t have access to Mendel, let alone later geneticists, and his ideas regarding heritablility (very understandibly) were crude and off base.
I don’t think we’re close to grasping all the implications of horizontal transfer–but one of the obvious implications is that Darwinian evolution, while it remains completely valid, may not capture earth’s life-history as completely as we thought. I’d like to think that if Darwin were alive today, he’d be all over this, trying to fit it into a new synthesis.
I share your sense of wonder about that. Here’s something:
The onset, over a period beginning about 5,000 – 10,000 years ago, of settled burgeoning organized communities is associated with the concurrent development of agriculture. Cultivating and storing massive amounts of food was easier and more predictable (actually more energy efficient from an “optimal foraging” standpoint) than hunting and gathering; and it simultyaneously enabled domesticated livestock management (grain feed), another food production benefit.
Biologists and anthropologists probably do not contend that Darwin is a complete answer, except perhaps regarding speciation and variation. The development of civilization as a social organizing feature of homo sapiens is not necessarily related to those mechanisms.
We, those who believe in science, have to be careful to credit Darwin at every turn as our understanding of evolution evolves. You did this well and I mention it only because I know that the boneheads in the ‘Intelligent Design’ camp would look at the title of this article and say, “See! Even scientists know Darwin was wrong!” They would of course not read the article, nor understand it if they did. Just wanted to point this out.
Exactly right. Origins of agriculture, origins of civilization are not genetically caused, rather are cultural in origin. It’s a whole ‘nother area, different form of adaptation.
Absolutely, yes. I fully expect that at some point creationists will seize on this concept and try to run with it as proof that evolution is all a liberal conspiracy. Just like global climate change. But the only way they can do so is to lie about it, distort it in some way. This is frequently their best and only weapon.
My dad taught evolution at the university level for 30 years in the south. I know how fundamentalists operate. My ol’ man fought it out with creationists back in the day often penning op-eds in local papers and always generating hateful responses via letters to the editor whenever he did. To his credit, he loved the fight and never backed down an inch. He knew truth was on his side and this gave him complete confidence in his little mission.
Good on him, and you. I’m reminded of people like Stephen J. Gould, or Loren Eisley, both college professors who did an incredibly great job of teaching evolution to readers of their popular books. They are both gone, and I don’t think anyone has stepped in to carry that torch.
You cite one example to support your disagreement; “The major development of a gene is by being built (invented) in one organism.”
Open to debate, . . . but even if accepted as a law of evolution, compare the level of importance of the development of any one gene, no matter how derived, to the origination of the nucleated cell, the incorporation of cellular mitochondria, or the acquisition of cellular mobility, for example.
I will argue that these are all major evolutionary steps that make such events as, to take another possible example on a larger scale, whether reptiles or mammals eventually develop the capacity to advance to a sufficient technological stage as to “irrevocably” dominate the planet, in comparison and from the impersonal view of the evolutionary process, a minor matter.
. . . And while I am certain that evolution is a valid theory, it does not attempt to account for the origin of consciousness in the Universe, as everyone should be willing to acknowledge
http://feedbooks.com/userbook/2988
The poison you are promulgating here is the mistaken assumption that Evolution has operating over it some Directed Purpose and that concepts such as “Vertical” and “Advancement” actually apply. Evolution is nothing more than the long series of binary Survive-or-Perish decision events WITH NO “INTELLIGENCE” or PURPOSE or DIRECTION behind it. To believe otherwise is to go right back to the Social Darwinism of the Scopes Monkey Trial. I am becoming of the opinion that the concept of Evolution is best dispensed with for no other reason that it is just, plain meaningless and misleading on many accounts.
I’m not promulgating anything like what you claim. “Advancement” never appears, in word or in concept. You’ve either not read the article, or not understood it.
With a knowledge of the genetic code we can now make cross-comparisons to bacteria and viruses to see if the DNA actually is more closely “related” to them than to any gene families “native” to the organism.
The fact that mtDNA and certain plasmids actually operate via distinct inheritance systems suggests that they were independently acquired. But there still is a lack of evidence for other phenotypic structures.
And in fact, incremental trial and error (rather than “stealing” or “eating”) is probably is the “safer” option. Organisms have a pretty effective system of breaking down consumed material to basic nutrients in order to avoid being infected or consumed by that being eaten. The nucleus acts as a firewall to prevent extraneous DNA from interfering with cellular functioning. Certainly there has been a some bacterial and viral DNA crossing that barrier…but there is not much evidence that it actually codes for productive structural features in the cell. Rather it may influence the rate and timing of the proteins involved in the production of those features.
I think that one needs to place such hypotheses in sound evolutionary frameworks by showing that the genetic systems involved are only explicable through the introduction of an independent genomic system.
In other words, if I have an oncovirus integrated in my genome that none of my relatives have then I have been infected, by horizontal transmission. But if it is present in my relatives, and not in others (one can look for genetic strains here) then it may be vertically transmitted.
Most of the features we know about are certainly transmitted and genetically modified vertically, thus the “horizontal transmission” model requires the stronger evidence. It has held up in one or two cases (mitochondria and plasmids), both of which have bacterial-like replication systems. But other complex features are produced by genomes protected by a firewall (the nuclear membrane) that assuredly is there to limit the introduction of foreign DNA and RNA into the genetic code. Most of the cases of such introduction (that have survived) are cases where there is repetitive sequences or short Tandem repeats that may have a role in regulation (speed and timing) but not produce any particular “features”.
http://whyevolutionistrue.wordpress.com/2009/10/29/controversal-paper-on-origins-of-caterpillars-debunked/
In some cases these arguments remind me of the old idea of a Greek Philosopher who thought that organisms were chimaeras of different organs that developed autonomously and spontaneously combined.