Do you mean, why would sex never appear? Well, consider...
Of the 3.9ish billion years life has been on Earth, for >90% of that time (the first 3.4ish billion years), life was simple, microbial, reproducing and surviving just fine without all that male-female jive. But then, relatively recently, something major supposedly happened (eg, massive methane release from ocean bottom), which upset the applecart, allowing multicellular critters (and eventually sex) to arise.
IIRC, it's estimated that most of the biomass on Earth today is still microbial.
Sex may be a big deal to us, but in the Big Picture, it doesn't seem all that necessary.
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Last edited by Mindship on Jan 18th, 2012 at 11:41 PM
Sorry I missed this thread and if I am convering something already covered (no way am I reading 6 pages on an easy to answer OP).
The REAL question is: why do we have males and females when hermaphroditic sexual reproduction (each member of the species has both or can function as a male or female) offers the best of all worlds including asexual reproduction in times of "island" organisms (meaning, there are none to reproduce with but there is still plenty of food around so they reproduce asexually). That would obviously be the most advantageous outcome for natural selection. It has all the perks of sexual and asexual reproduction with none of the bad side-effects. The only proper response I have seen to this is a comment about over-population. Nonsense. Evolution should take care of those that can reproduce too quickly. Now, someone may say to that, "which is why we ended up with most higher species being sexual, not hermaphroditic". Nonsense. That eliminates thousands to hundreds of thousands of possible solutions for what evolution could do BESIDES non-hermaphroditic sexual reproduction. Why would you automatically assume the one solution to overpopulation is sexual reproduction? Why not assume a mating ritual or mating conditions that reduced the probability of reproduction? There's plenty of rituals found in nature. There are plenty of conditions, as well.
Just saying that there is a better question than the one in the OP.
There is a perfectly valid evolutionary reason for sexual reproduction "working", btw. I just don't see why it ended up being non-hermaphroditic.
Evolution doesn't get you the best system, just a system that works.
I can't think why hermaphroditic organisms would massively out reproduce sexual ones. The benefit is rather niche (when you have a group of one sex localized in one place) and populations falling into that niche are just going to die without reproducing.
At the same time more genitals means more potential for infection and damage so they would be slightly selected against.
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But I thought that hermaphrodites, at the worst, co-evolved with binary species. Meaning, the "best system" was already place at or before the binary system. Meaning, in this instance, the "best system" should have been selected for as it would be superior to the binary sexual counterparts.
Powers of two.
Instead of one mother and father, you have one mother and one father in each. Meaning, you double the output. This cannot be sustained so evolution would have to eliminate those species that produced too many offspring.
You're thinking of genitals in terms of Homo sapiens. However, that's still a problem of immune systems rather than increasing the "risk front". Additionally, it is partially a function of volume (and surface area) rather than number. Lastly, it would be easily selected for which is why snails and slugs are so numerous (I believe they are second to insects in that regard).
Some respond that we didn't get complex/sentient* hermaphrodites because snails and other types of hermaphroditic multicellular organisms were already so well adapted to their environment that significant change is not necessary. This is probably the most plausible and I can settle for this. Snails are one of the oldest species known.
*Because sentience does not equal higher evolution.
This occurred to me as well but it does mean we can say (a bit tautologically) that evolution picks sexual species because they outcompeted the hermaphrodites.
Ah, yes, while we're restricted to the plodding pace of the Fibonacci sequence.
The practical one makes some sense in terms of competing against hermaphrodites. If you need to raise children and you need to get food its beneficial to have sexes specialized for those tasks. I'm not sure if hermaphroditism prevents sex differentiation, though.
Evolution doesn't really need to do that as I understand it. The predator/prey relationship deals with population, its called the S-curve. You get a pair of slightly our of phase sine waves as the predators benefit from abundance of prey until they start forcing the population down there aren't enough to keep it from rising again. A hermaphrodite predator would be able to keep up.
I guess we could be blob people and it wouldn't matter so much.
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Graffiti outside Latin class.
Sed quis custodiet ipsos custodes?
A juvenal prank.
Well, it would appear that evolution picked both but evolution "got it right" with hermaphrodites much sooner...which is why some types have been around for 600 million+ years.
The majority of those arguments are microscopically based. While Dawkins goes as far as to say "male equals giving information and female equals keeping that information". While I do not hold that microscopic reasons for reproduction are mutually exclusive to macroscopic actions, I do hold that my approach is much more macroscopic than the context of that article.
We end up with birds that have long beaks and tongues that can pull out the snail's meat from their shell. Meaning, because things like snails have been around so long, the purely "sexual" species evolved around feeding practices concerning snails. This is another testament to how permanent hermaphrodites can really be. They get the benefit of exchanging information (refer back to Dawkin's explanation) and genetic diversity but they also get the benefit of asexual reproduction in times of need. They are the "have your cake and eat it too" kinds of species. To me, it just seems like the ultimate result of natural selection when it comes to sexuality.
This is part of what I mean. Some species were very successful because they flood their predators with so many opportunities to "feed" that there are never enough predators to eat all of the offspring. This occurs with sea turtles: there are too many babies trying to reach the ocean that the predators cannot eat them fast enough. However, it is balanced enough that enough of those turtles are eaten that they do not eat too much as they grow in the oceans.
The balance can be thrown out, for sure and this is what I was talking about when I said nature would eliminate those species. Too many are created that not enough predators can consume them. Then they take over until their food source becomes scarce so their number dwindle down or they evolve to better control their population (like selective breeding...rituals...etc). This has happened several times and I am reminded of the Devonian period taking care of much of the homogeneity through an explosion of speciation.
Well, personally, I am okay with being turned into a hermaphrodite. Sure, it would be weird, strange, and/or devastating at first. But we would get used to it.
Not a blob, though. Yuck. Reminds me of the breeding pile on South Park. Was it the "they took our jobs!" episode?
I was hoping that humans could master DNA and DNA expression to the point to where we could create "perfect" creatures that are adapted to pretty much any environment on the earth. Take the best of each super species and combine it into a super smart creature...bam...super perfect "humans". I think we would resemble reptiles. We may even have chitin skin.
Combination of two sets of chromosomes instead of just one. More perks in that direction.
__________________ Recently Produced and Distributed Young but High-Ranking Political Figure of Royal Ancestry within the Modern American Town Affectionately Referred To as Bel-Air.
Jan 17th, 2012 10:00 PM
...oh man, the image that flashed through my head when I read that...
