braces_for_impact

Since you're alive, then obviously your ancestors are all dead right? Mom, Dad, Grandparents, etc?

Edited for dumb mistake.

Doubting Didymus

If you really want a genuine answer to this question, I wrote this small piece of amateur hot air a while ago, which deals with this topic.

Read it, don't read it, at least I had an excuse to drag it out again.

Does evolution always favour complexity?

Short answer: no.

From the time of Aristotle until only comparatively recently, one of the central themes of biology was that of the 'great chain of being'. Usually derived from natural theology, this is the idea that all life can be placed on rungs of a single spectrum from small, simple and stupid to big, brainy, and bogglingly complicated. Humans are, of course, always placed at the top of this ladder. The advent of the theory of evolution might have challenged this anthropocentric view of life, but really did not. The great chain of being persisted in the form of the idea that evolution favours complex, (and large, and smart, and generally human-like), organisms. Humans are again at the top of Natures Most Favourite Things list, being the smartest and the most complex organism of all. Could it be any other way?

Well, yes it can. There is certainly nothing inherent in the theory of evolution by natural selection that should make complexity a goal. The only goal is reproductive fitness, and few biologists could deny that simple organisms are amongst the most fit of all. Insects are easily the most successful animal, and few would argue that bacteria, the simplest known self sufficient reproducers, are definitely the most common, and probably the most fit, of all known life. 'Keep it simple stupid' has shown its value in the form of tiny, simple, and highly fit bacteria. That'?s right! Evolution has favored kissing with germs.

Another example of evolution favouring simplicity is the atrophication of unnecessary system components, such as the reduction and removal of eyes in cave dwelling fish, and the way that sea squirts eat their own brains when they settle on a rock and become sedentary. This phenomenon is often likened to tenured professors. They are quick and brainy in their youth, but soon enough they settle in an institution and, not needing it any longer, devour their own brain. The lesson we learn from these cases is that complexity is not only NOT always inherently favoured, but is frequently a fitness detriment: a resource expenditure that does not pay its way.

Generally, simplicity is good. I drink coffee with a cup, not with a solar powered electric antigravity intravenous tube system (a guy can dream, though). When you have a goal, be it a caffeine hit or a huge gaggle of descendants, doing it simply is often much better than doing it in a roundabout complex way.

Does evolution ever favour complexity?

Given the advantages of simplicity, can it be said that evolution would ever favour a complex organism over a simpler form? There are a few theoretical conceptual frameworks that might provide for this.

First, the Red Queen effect. Named after the queen from alice in wonderland who had to run as fast as she could just to stay in the same place, the enigmatically titled red queen effect refers to evolutionary arms races. The cheetah must be fast to catch gazelles, and the gazelles must be fast to outrun the cheetah. Evolution in both populations will favour faster and faster individuals, yet neither ever gets an upper hand on the other, or there would be extinctions all round. This effect is known to drastically change features, and can theoretically apply to all sorts of things: weapons might be locked in an arms race with armours, potent chemical poisons locked in an endless challenge with their antidotes in prey species. Two species of bacteria might develop more and more sophisticated attack, defense and reproductive systems, each simply struggling to keep up with the other. Fenced in by the economics of simplicity, it may be that the only way to go is up, to develop more complex reproductive strategies, become larger, and evolve all the necessary equipment to allow it to happen.

Why would complexity be a bonus in this case? Well, apart from making intuitive sense, someone?s spelled it out in a theory, in this case one W. Ross Ashby's Law of Requisite Variety, which goes like this:

The larger the variety of actions available to a control system, the larger the variety of perturbations it is able to compensate.

For a detailed run-down see: this page . This is the gist, as it applies to evolution:

Evolutionary systems would be fitter if they could have greater control over their environments, because it improves their ability to survive and reproduce. The more control the better, and the more organization and interwoven complexity the more control the organism has. A bacteria is great for randomly swimming around, absorbing nutrients from its surroundings and mindlessly replicating, but most metazoans are a veritable swiss army knife, incorporating many solutions to hundreds of different natural problems by comparison. Since incorporating a solution for EVERY problem nature throws at populations is probably impossible, evolution might exhibit a constant upward trend.

Evolutionary history: there IS an upward trend. Why?

The fossil record, which started the whole evolutionary ladder of life bruhaha in the first place, DOES demonstrate that life has become more complex on average over time. There are a number of perspectives that people like to look at this from.

One important player is an idea I'll refer to as the 'drunkards walk'? hypothesis. The basic idea is that if you take a bunch of randomly moving drunk men and place them together in the center of a room they will naturally radiate outwards. Nothing is driving them to move away from their start location, but basic statistics will ensure that some of them move out more than they move back, and you end up with a gradient. Most drunkards move out as much as they move in, and end up with no net movement, some will move out a little more than they move in, and some will randomly move almost entirely out, giving you your probability curve. Now, what happens if you do the same thing, but start them out against a wall? You'll find that on average they move away from it, based solely on random motions. Most will stay put again, many will move partly out and partly back, and you end up with a probability curve in which the average distance from the start location has increased.

This is not empty hypothesizing, either. The work of one Daniel McShea in the last decade has been focused on empirically demonstrating that the predictions of the drunkards walk are, in fact, what we find. He ran a very intricate and involved set of experiments on vertebrate backbones, measuring the evolving complexity of the various parts and how they interacted.



From:

Dan McShea and the Great Chain of Being:
Does Evolution Lead to More Complexity?
by Frank Zoretich

In the image you see, figure A is the trend we should see if all of evolution always favoured complexity. Figure B is what we should see if no driving force is present. What we DO see looks most like figure B: mostly simple organisms that persist throughout history from their origin, with a gradual increase in average complexity on top of that. Does this mean that the drunkards walk hypothesis is the explanation? Not quite.

One problem with the drunkards walk is that, in the total absence of a pressure favouring complexity, a return to simplicity is favoured. We see this in atrophication, and can theorise about it with respect to its economy. Even if there is no active drive, there must at least be a fitness benefit strong enough to preserve the complexity once it appears. McShea is well aware of this, which is why his hypothesis refers to a 'passive trend', rather than an absence of any benefit. Once the population has evolved complexity for whatever reason, there must be enough of a benefit to keep it there. Given this, it is hard for me to see why that selfsame fitness benefit would not simultaneously count as a selection pressure. I confess I do find it hard to swallow the idea that the myriad benefits of metazoan complexity are merely neutral to natural selection. In my eyes, complexity should count as a kind of ecological niche, opening new doors for those life forms with the right stuff, lifting them out of the bacterial rat race and into the unexplored and competition free world of eukaryotic organisms.

In any case, McShea?s work sparked a lot of interest in this area and a lot of data is being gathered. There is a growing body of opinion that seems to support the idea that no universal selection pressures for complexity exist, and that increases in complexity are not significantly more common than decreases, on average. The important thing to remember is that even if complexity is not universally better for survival and reproduction than simplicity, we should still see a general increase in the mean complexity, simply due to the Brownian motion of the drunkards walk effect.

Amaleq13

Man did not evolve from monkeys. They both evolved from a common ancestor. This is a classic misunderstanding that really cannot be corrected too many times, IMHO.

You may now return to the more substantive posts above and, eventually, below.

Roland98

You may also want to check out this thread, which discussed the evolution of single cell-->multicellular organisms, and why single-celled ones still exist.

MrDarwin

Because dinosaurs didn't evolve from amphibians, at least not directly. (In fact they didn't evolve indirectly from amphibians either; numerous groups of early tetrapods have been labeled "amphibians" out of convenience but they were quite different from modern amphibians, all of which are descended from just one of these groups, and it was not the same group of early tetrapods that reptiles evolved from.)

But reptiles did evolve from amphibian-like critters, and those amphibian-like critters did evolve from fish, and we have some pretty darn good fossils of those part reptile-part amphibian and part amphibian-part fish critters.

Biff the unclean

That's exactly what you would have seen six to seven million years ago. At that time there were 58 species of great ape that we know of.

faust

I just gotta jump in with one of my favorites.
"If god created Man from dirt, why is there still dirt?"

extremophile

I did not follow the entire thread, anyway, something I think that may be interesting. The article"The evolution of dinosaurs" by Paul Sereno (including birds), despite of the article itself, shows a lot of transitional forms between various dinosaur groups.

About crossbreeding itself, I think that is interesting the case of the interbreed between lions and digers, accepted as different species, altough they have half-fertile offpring (only fertile females). Eventually we show to creationists stages of early speciation, like ring-species, eco-species or sub-species, that can yet interbreed and produce 100% fertile offpring, although that is very rare, or even observed only in captivity. To these samples, they say "that shows that they still are the same species". When you point two close related species that can't produce offpring, or fertile offspring, that "proves" that they're created species made to not mix up. But this case, with 50% of fertile offspring, technically would provoke some genetic flux between the two species, if occurred in the wild. As they see subspecies that breed in captivity producing fertile offspring as the same species, this breed is, undeniable, IMHO, a example of a "half" speciation, althought they're generally accepted as separated species.
Of course, that is a useful example to show only to creationists that do not accept any level of speciation, and unuseful to those who accept speciation under the same "kind", whatever it is.

Jet Black

they are distant cousins. Remember that just like family trees, evolution has branching lineages. even creationists have to admit this if they believe that all life today diversified from a set number of kinds.

Jet Black

well there are, as has been pointed out. Then we also have part reptile-part birds (Archaeopteryx and friends), part reptile part mammal (the Therapsids), part human part chimp* (George Bush) and so on.

*warning: this is a joke.