Convergence
by BradfordMark Vernon authored Not so highly evolved, an article worth reviewing, both for its analysis of Richard Dawkins and for its commentary about an evolutionary phenomenon known as convergence. The article begins:
The 2009 Darwin celebrations are officially under way, now that we are halfway through Richard Dawkins' flagship TV series, The Genius of Charles Darwin. But I can't help but feel they have not begun well. Dawkins' exploration of the science seems to be driven mostly by his desire to score atheistic points: this is not evolution as survival of the fittest but as zero-sum game.
I have not seen the TV series but based on prior behavior a charge that Dawkins is using science to score atheistic points comes as no surprise. If Dawkins is indeed guilty as charged he needs to be taken to task. The Trojan Horse imagary is apt for all who would use science to introduce a side agenda. Vernon also had this to say:
Convergence raises the possibility of directionality in evolution. This is anathema to the old school. Strictly speaking, even to talk of adaptations being advantageous is to risk a false sense of teleology. The sense of "advantage" only comes because we have hindsight. As Stephen Jay Gould put it: according to this interpretation of evolution, if you re-ran the "tape of life", life would look very different.
Convergence challenges this, because in a way, evolution has already re-run the tape of life several times, and it looks strikingly similar. The implications that might be drawn from convergence is what Conway Morris' new book explores. One of the essays, entitled Purpose in a Darwinian World, is written by the philosopher of evolution, Professor Michael Ruse.
Intelligent Design generally incorporates both directionality and purpose. Apparently so does the new school on convergence. Yet Ruse would readily argue that "Darwinian processes "design" organisms to exploit aspects of the natural world." More:
However, the phenomenon of convergence is used to take the possibility of directionality a step further. For what happens if you consider not only elements such as air, water and land to be environmental niches that Darwinian processes can exploit, but elements such as culture and intelligence too? The old school believes that evolution itself creates the niches of culture and intelligence. But what if instead of creating these niches, evolution is exploring pre-existing realities that in this respect can be thought of as analogous to air, water and land?
It sounds pretty speculative, until you consider, say, mathematics. At least some human's brains are capable of doing mathematics. Perhaps some other animal's brains are too. But is mathematics created or discovered? It seems more natural to think of mathematics as existing regardless of the presence of human beings, as, say, the laws of nature presumably exist in the universe too. So maybe the evolution of culture and intelligence are not just by-products of humankind's evolution as a social animal. Perhaps, they are also ways of discovering and exploring pre-existing realities. Conway Morris himself has tentatively suggested that the brain could be thought of as an evolving "antenna" that detects mentality which is itself independent of human intelligence.
Processes can become so intertwined that at times it is unclear which process is in the driver's seat. For example, humans are in a position to influence how our planet evolves. We can bring about extinctions, preservations and alter ecology. But I would think that mathematical principles would exist if no humans were around to appreciate or comprehend mathematics. So I would side with Conway Morris in believing that the human brain detects "mentality" which is independent of human intelligence.
August 25th, 2008 at 10:13 am
Is this controversial? It seem obvious that intelligence and culture effect the fitness landscape and thus effect future evolution. Even without intelligence life has always effected its environment, the very fact that there are hunters and prey and a food chain should be all anyone needs to realize that evolution has a lot of feedback. Life effects evolution.
My cultural anthropology teacher always stressed how much the environment shapes culture. Similar environments often generate similar cultures even when they are relatively isolated. First and foremost any culture must provide for the survival of its members and what survival techniques work is largely about the environment. If he is suggesting that the common belief is that culture is formed by life independent of the same environment that created that life then I guess I'd have to disagree. First, I'm not aware of anyone who thinks that, and second if anyone does think that it seems wrong.
I would certainly think that culture would be highly constrained in its choices in a way similar to how life is constrained in what can evolve. As I said only those cultures that ensure the survival of their members will work. Isn't this high degree of similarity between biotic evolution and cultural evolution a major factor of the whole "meme" concept?
I mentioned that evolution has a lot of feedback, that continuous cycle of cause leading to effect which is itself another cause certainly does make it hard to untangle. On an unrelated note, this sort of feedback is also a critical component of the human brain, without it intelligence would be extremely limited if not impossible. Perhaps any system with a high degree of feedback effecting the result would exhibit the appearance of intelligence and thus design.
I think in general Vernon is waxing philosophic about a phenomenon with a much simpler explanation. What works works. In order for something to evolve from a precursor state to a final state it must provide benefit. Many macro features like pointier teeth would provide benefit in a wide range of environments. Why wouldn't they appear over and over again? What works works. None of this challenges Gould's assertion that the tape would be very different if replayed, its just a question of where you replay it from. Stick a hundred flat-toothed cat species in an otherwise identical environment and there's a decent chance one of them will end up with pointy teeth, but go back to the very beginning and the odds of getting a cat at all from your self replicating proto-life seem very slim.
Comment by Todd Berkebile — August 25, 2008 @ 10:13 am
August 25th, 2008 at 11:39 am
Old school? Convergence is discussed by Darwin in "Origin of Species" as *evidence* of Natural Selection. Darwin provides examples such as the rhea and ostrich, agouti and rabbit, coypu and beaver, capybara and muskrat. We also have Darwin's finches which evolved to occupy the finch, warbler, ground, tree, woodpecker, leaf-, bud-, insect-, grub-eating and tool-wielding niches.
And yet, we can still determine their ancestral relationships.
Darwin: It is incredible that the descendants of two organisms, which had originally differed in a marked manner, should ever afterwards converge so closely as to lead to a near approach to identity throughout their whole organisation.
So a dolphin may develop the streamline shape of a fish—convergence through natural selection—but still exhibit a clear relationship to other mammals.
Comment by Zachriel — August 25, 2008 @ 11:39 am
August 25th, 2008 at 2:28 pm
Faz Rana gave a good lecture on the UC series about convergence as evidence of design (OEC, to him).
Here's a brief article on his views.
http://www.reasons.org/resourc...
But, from the OP, Vernon seems to be saying something much more profound about evolution. Ot makes me think I may have to explore Conway Morris' writings.
It has long been said that our brains don't seem to be the product of natural selection. We should be able to do the math necessary to leap a stream or catch an apple, but to decipher the cosmos?
As Zach says, fish and dolphins may evolve similar body types in similar environments because of the demands of the environment and "what works is preserved".
When did the ability to do Minkowskian geometry, for instance, "work"?
If we are filling the empty barrel, accommodating our niche, then is there an invisible niche of mathematics and logic into which our brains have evolved?
Does that sound like philosophy? It's all philosophy.
Comment by Pez — August 25, 2008 @ 2:28 pm
August 25th, 2008 at 2:33 pm
Vernon,
Convergent evolution reflects nothing more than the limited set of solutions to any environmental problem–two species converging on the ideal morphology to exploit a particular niche or lifestyle. To extend a previous comment, an ichthyosaur (extinct reptile), a dolphin (mammal), and a tuna all arrived at essentially the same solution to the problem of how to move quickly through the water. Why should this suggest foresight or directionality rather than the evident need for a streamlined shape to solve this problem?
Comment by David E Levin — August 25, 2008 @ 2:33 pm
August 25th, 2008 at 3:14 pm
Here's Rana
http://www.youtube.com/watch?v...
Comment by Pez — August 25, 2008 @ 3:14 pm
August 26th, 2008 at 1:08 pm
So it's pretty much agreed that Gould was probably wrong about his "rewind the tape" prediction?
Comment by chunkdz — August 26, 2008 @ 1:08 pm
August 26th, 2008 at 5:50 pm
David Levin,
Perhaps a clue lies in the fact that you feel the need to explain evolution as a "solution" to a "problem". Why do you feel that evolution is about "solving problems"? And why is biology evidently so good at "solving" these "problems"; so good in fact, that it repeatedly finds the same "solution" to the same "problem"?
And is it really a "problem" to be too fat to swim fast? Is it really a "problem" not to be able to see? Do these really require "solutions"?
Or to expand on Pez's comment above, is not understanding Minkowskian geometry a "problem" that needed a "solution"? If we rewind the tape of evolution, would Minkowskian geometry be an expected "solution"? Would we expect that other higher mammals would reach the same "solution" eventually?
Comment by chunkdz — August 26, 2008 @ 5:50 pm
August 26th, 2008 at 6:14 pm
Here's a thought for those who like to think about such things.
We've all heard, although I'm not going to Google the reference right now, that DNA is the record of what an organism is doing. It is not the determiner but the result.
This seems appropriate when we think of all the different, morphologically indistinguishable moles with such vastly different genomes. Or in the cases of convergence as Faz Rana has described above. Frogs on different continents, from two different lineages, develop so as to be virtually identical. It seems as though nature demanded that there be both arboreal and terrestrial frogs on both continents - genomes notwithstanding.
Or that there were going to be freshwater river dolphins - even if they had to evolve four time independently from four different sets of ancestors.
There is no need to rewind the tape because we have several playing simultaneously and we can see the results have converged on the same "solutions". Since asking the right questions is always key, how were the problems established for which these solutions were offered?
Comment by Pez — August 26, 2008 @ 6:14 pm
August 26th, 2008 at 6:57 pm
Hi Pez,
I'm glad you mentioned frogs. Not only are they a great example of convergence, but one has to wonder why the frog design convergently became the "solution" to so many different "problems". It is interesting that a body designed for water/land should end up as the "solution" for the "problem" of how to survive in the arid Australian desert, and the "solution" for the "problem" of surviving the frozen arctic.
Comment by chunkdz — August 26, 2008 @ 6:57 pm
August 27th, 2008 at 7:00 am
Gould tended towards one edge of the spectrum between contingency and determinism. There is little doubt that if we would "rewind the tape", we would be surprised by the differences, but we would also probably recognize many similar forms.
You are actually hitting on an important point. Life is fecund, and will tend to fill whatever available niches are available to it. Therefore, it is not surprising that a successful organism (such as the frog) will evolve to fill a variety of niches. Or that similar organisms (such as different dolphin lineages) will evolve to fill similar niches.
Comment by Zachriel — August 27, 2008 @ 7:00 am
August 27th, 2008 at 1:30 pm
Zachriel,
That's a bit of a non-answer, isn't it?
Clearly, chaos tells us that the tape will not play back exactly the same way.
But more interestingly, it would seem that the genetic toolkit of life is uniquely qualified to produce what it produces. Different pathways, but with a goal in mind - whether that goal is a frog, or a flying squirrel, nature seems determined to reach it.
Of course, we're not talking about one lineage evolving to fill a variety of niches. We are talking about different lineages ending up with nearly identical designs. The tape is played back, and we still get flying squirrels. The tape is played back and we still get foxes bears and wolves. Nature wants to make flying squirrels, foxes, bears, wolves, etc. etc. etc..
This begs the questions… Does nature want to make mathematics? Does nature want to make Mozart symphonies and Donne sonnets? Does nature want to make consciousness?
Comment by chunkdz — August 27, 2008 @ 1:30 pm
August 27th, 2008 at 2:50 pm
In the examples provided they are different lineages, but related branches that then confront similar environmental challenges.
Only if you start the playback after mammals evolve. Otherwise, you might see dinosaurian tree gliders or something else entirely.
Comment by Zachriel — August 27, 2008 @ 2:50 pm
August 27th, 2008 at 4:05 pm
Zach,
Or different environmental challenges. Tropical or arctic, lake or desert, the frog is a goal of nature regardless of lineage or environment.
This is merely an article of faith for you. Science, however, shows us examples of convergence stemming from the very earliest branching of metazoans to the present day.
Comment by chunkdz — August 27, 2008 @ 4:05 pm
August 27th, 2008 at 7:38 pm
And if the metazoan LCA isn't rewinding far enough for you, convergence goes even further than that.
Convergent Evolution of Gene Circuits, Conant and Wagner, Nature Genetics July 2003, Volume 34, Number 3, pg. 264-265.
From the abstract:
and the summary:
Comment by chunkdz — August 27, 2008 @ 7:38 pm
August 27th, 2008 at 8:56 pm
They diverged from a common ancestor and adapted to a variety of environments.
Not at all. The scientific evidence indicates that the end the dinosaur was a highly contingent event.
Convergence has been important evidence for Natural Selection since Darwin first proposed his theory.
Comment by Zachriel — August 27, 2008 @ 8:56 pm
August 27th, 2008 at 9:25 pm
Zach,
Yup.
We're just rewinding the tape of evolution, not the entire cosmos. The evolutionary niches remain. The only question is will this produce flying squirrels again, or saber toothed jumping shrews to fill the niche.
Luckily, science has answered this question to some good degree.
Yup. Convergence is evidence of Darwinism.
And so is Divergence.
And so is Stasis.
And Parallel Evolution.
And Extinction.
Ooh, the power…
Sorry but I'll follow the evidence where it leads, not fit the evidence to my worldview.
Comment by chunkdz — August 27, 2008 @ 9:25 pm
August 29th, 2008 at 10:30 pm
But you can't rerun the history of life on Earth without including all the contingent events involved. That's the point. The history of mammals would look quite different without the unexpected demise of the dinosaurs.
Yes, once you have large terrestrial plants, you're going to have arboreal habitat.
Um, squirrels and shrews are both mammals. I suggested tree-gliding dinosaurs. Though mammals and dinosaurs could inhabit similar habitats, they are different in many respects (though both are amniotes ).
In any case, I'm not sure what point you're making. I agree that certain morphological forms are to be expected because of the available range of habitats. But I think it is also quite clear there would be many surprises if we reran the tape of life. The question is how much is contingent and how much is determined. There are no simplistic answers, and hand waving doesn't really add much to understanding the problem.
Have you actually read Origin of Species or a basic text on evolutionary biology? Most of those aspects of historical evoluton are discussed by Darwin and have been researched extensively since then.
Comment by Zachriel — August 29, 2008 @ 10:30 pm
August 29th, 2008 at 11:12 pm
Zach,
I just said that.
Yes.
Non-sequiter.
Yup.
The dinosaurs died.
Yes, (yawn), dinosaurs and mammals are different.
If you're suggesting that we rewind the history of evolution AND things like comets hitting the earth, then all bets are off. We are talking about the same niches being filled by lineages evolving through random mutation and natural selection. No matter how many times you rewind the clock, the comet is still going to hit. All things being equal, would evolution fill the niche exactly the same way? Make sense now?
Apparently not as many as we thought. Apparently, there is a pretty specific set of possibilities.
So instead of defending your circular reasoning you simply retreat to your ivory tower.
What a condescending dork you are.
Comment by chunkdz — August 29, 2008 @ 11:12 pm
August 30th, 2008 at 2:13 pm
No.
I take that as a "No." The reason I asked is because this issue is discussed in Origin of Species and most basic textbooks. Even if two lineages are closely related, they will still not "fill the niche exactly the same way". There is a legitimate question as to the relative influence of contingency and determinism.
Comment by Zachriel — August 30, 2008 @ 2:13 pm