Evolution and Sex - The elephant in the room

Originally posted by BobbinHood
reply to post by madnessinmysoul

 

That's the wonderful thing about science, it's entirely opposed to the idea of personal belief.

And rightly so.

And today, science is a poor guide to the nature of reality itself.

That has to be the weirdest statement I read on ATS today. You're kidding, right? Science is based on logic, rationality, and evidence...which kind of means it's based on reality. Science is the analysis and observation of nature and the universe. It is exactly what you claim it isn't: A guide to nature and reality.

It might not be a complete guide, but at least the chapters we filled are based on fact. Compared to religion and spirituality which is entirely based faith without any proof, logic, or facts. Given what we know about reality (thanks to science), religion is a pretty poor guide for anything but (some....but not all) moral values based on fictional stories.

Let me ask you this: What's your guide to nature and reality?

reply to post by MrXYZ


I think you misunderstood my statement. I just mean that there is currently no good theory of everything. I mean reality on a fundamental level, that is all.

You read it as nature AND reality. What I said is the nature OF reality.

Of course science does a good job of describing the way things are. I was simply saying that when you get right down the fundamentals of it all, it falls short.

Well....I agree, we don't have a theory of everything (yet).

However, we do know about evolution, just like we know about gravity and thermodynamics. We know how it works

reply to post by Gaspode

Your question is even harder than you think it is. The mechanical development of penises, vaginas and other sexual paraphenalia is pretty easily imagined, after all. The real difficulties--the real elephants in the room--are the questions (1) why sex exists in the first place and (2) how the thing that had to evolve first, before sex as we know it could start to happen, came into being.

The tendency to fix on obvious mechanical issues reveals the scientific ignorance of those who defend creationism and so-called 'intelligent design'. Knowing and understanding so little, they miss the real problems of evolutionary theory and focus on mechanical trivia of the sort they can understand.

The reason we don't know the answers to the above questions is because no-one was around to watch sex and meiosis evolve, and because we can't reproduce that evolution in a lab--not yet, anyway. That doesn't mean they are hopeless mysteries. Actually, we have a pretty good idea when, how and why they came into existence.

Here are the answers, and inter alia, the answer to your question about the evolution of--ahem--copulation.

*

The original replicators, the ancestors of life, were probably single molecules of something like RNA. Such organisms still exist; a virus is nothing but a twist of RNA or DNA in a protein jacket--one molecule enclosing another.

From these primitive beginnings, more complex organisms evolved, in which the original replicator molecule was shielded from the environment and sustained by other chemicals within a protective envelope. In these prokaryotic organisms, the original replicator molecule cannot interact directly with the environment to form other replicators; instead, the whole organism has to replicate, ingesting raw materials from outside the cell wall and using them to make a daughter cell based on the 'instructions' contained in the the replicator molecule. This is ordinary cell division, or mitosis.

Single-celled organisms don't do sex, but even they have ways of exchanging genetic material. Such mechanisms evolved very early in the history of life on Earth, showing just how important mixing and shuffling genes is to the continued survival of all species.

But mitosis isn't just about single-celled organisms. It also makes possible the existence of multicellular organisms. The most primitive of these are slime moulds, sponges and the like; clumps of identical cells, which sometimes act like a single organism and sometimes like a collection of many organisms.

In time, these primitive organisms evolved into sophisticated collections of interdependent cells, each kind of cell specialized to a particular task. Thus animals and plants came into existence. The first of these still reproduced by cloning and budding.

But here, a complication arose: plants and animals, unlike unicellular organisms, take time to develop to maturity and reproduce. And in the time it takes for a generation of any plant or animal species to turn over, dozens (or thousands) of generations of single-celled organisms can be born and die. Early plants and animals, therefore, evolved much more slowly than the single-celled beasts that surrounded them.

Now, to a single-celled organism, a plant or animal is simply a large collection of organic matter--food--handily clumped together in a single space. Their emergence provided an opportunity the prokaryotes were quick to exploit. Thus was born parasitism. Of course, plants and animals could evolve defences from these single-celled predators; but the parasites evolved so much faster that the big guys were left far behind in this arms race.

The answer to parasitism was the shuffling and recombination of genetic material through the process known as meiosis. As I said, we don't know how meiosis evolved, but there are credible hypotheses. For reasons mentioned earlier, experimental validation remains a difficulty.

However, once meiosis evolved, the merely mechanical objections you raise to the evolution of sex are really quite trivial. Don't forget that life evolved in water. Do you know how most fish have sex? The female excretes her eggs directly into the water. The male ejaculates a cloud of milt (fish semen) on top of them--also, directly into the water. No penises, wombs or vaginae required--just gametes. And fish are pretty sophisticated beasts. More primitive multicellular organisms were probably doing the same thing from very soon after the evolution of mitosis.

From there on, the rest of the evolution of sex is simply the development of refinements to ensure fertilization takes place. It is quite easy to see how penises, etc., evolved--just as it is easy to see how eyes evolved--because the different stages in such evolution are illustrated by numerous species that still exist and thrive today.

All that remains to be said about this 'elephant in the room', then, is that citing the mysteries of sexual evolution as an argument against evolutionary theory is (a) not a proof of creation in the first place and (b) nothing but a tired old God of the Gaps argument in the second place. Science has a long history of invalidating such arguments; it is astonishing that creationists still keep on proposing them. Some people never seem to learn.

reply to post by Astyanax
^^

my response to the question "why does sex exists" would simply be "to fight of parasites", but such an oversimplified an ultimately empty response is no match for one of the most eloquent and carefully selected implementation of the various concepts involved in neoDarwinism I have yet read on this forum or anywhere outside of the expertise of the legendary writers of evolution. I am impressed beyond reason that one poster is able to illustrate the reasoning of Maynard Smith, Hamilton, and GC Williams all in a few hundred words without so much as missing a single general point of emphasis relevant to the phenomenon of sex and the history of evolution.


I can only assume you are either in postgrad or undergrad studying in some capacity genetics or biology.