Post #193,227
2/6/05 2:04:39 PM
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Re: Welcome
Yes, developmental biologist. You know, eggs, sperm, mitosis, meiosis, embryogenisis. Cynical fellow, arent you?
-"I think animal testing is a terrible idea; they get all nervous and give the wrong answers."
"The 2 most common elements in the universe are hydrogen and stupidity."
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Post #193,250
2/6/05 3:42:38 PM
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He has past cause...
An ex-member was very fond of creating lots of accounts, trying to get people to believe they were real, and then having them argue with each other.
This got old. Fast. Particularly the bit where the alter-egos persecuted the original.
But you're obviously not him. Too verbally adept.
Welcome. It'll be nice to have someone around who knows more biology than I do. (Mine is all by osmosis. My wife has a PhD in biology - she studied flower development.)
Pointers to neat developments in biology go into Science, complaints about what this administration is doing to NIH go into Politics, discussions about Creationism are avoided but can go into religion, various hobbies and interests can go in appropriate places.
If you haven't done it, I recommend going into Edit Preferences and chooding to see new posts only, and only forums with new posts. Then take forums that you're not interested in, look at the "mark forum read" link, edit the timestamp into the distant future and submit that.
That way you'll only see the forums/posts that you want to see.
Cheers,
Ben
I have come to believe that idealism without discipline is a quick road to disaster, while discipline without idealism is pointless. -- Aaron Ward (my brother)
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Post #193,261
2/6/05 4:08:34 PM
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No I'm not him...I'm a her
And thanks for the pointers to maneuver around the board. Very helpful.
-"I think animal testing is a terrible idea; they get all nervous and give the wrong answers."
"The 2 most common elements in the universe are hydrogen and stupidity."
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Post #193,275
2/6/05 5:18:59 PM
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Cool, there is a slight imbalance in these parts..
I have come to believe that idealism without discipline is a quick road to disaster, while discipline without idealism is pointless. -- Aaron Ward (my brother)
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Post #193,334
2/6/05 10:41:07 PM
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Men are parasites ;-)
Or so goes my theory of how we came to have two distinct sexes.
I've never seen anyone else put this forward. I've also never had anyone tell me that this theory was obviously stupid. So here it is for your amusement.
Evolutionary textbooks talk about sexual reproduction and the speed with which it lets a population adapt to changed circumstances. Which is all find and dandy, but doesn't explain why we are not all hermaphrodites like the earthworms are. After all hermaphrodites get all of the benefits of sexual reproduction and also manage to reproduce twice as fast for the same effort (assuming that one parent bears the bulk of childrearing responsibilities, which is certainly true for many species).
So here's my theory about why we're not all hermaphrodites.
Consider a population of hermaphrodites. To this population add a small number of cheaters that we'll call males. These cheaters have sex, but don't get pregnant, and then have sex with someone else. In effect they are parasites on the main hermaphroditic population who trick their victims into having kids and deny them half their reproductive future.
I believe that c. elegans looks like this.
Now suppose that these parasites become very efficient. Then hermaphrodites have to choose between two strategies. The first is to try to be hermaphrodites, try to avoid males and find another hermaphrodite. The other is to just give up, breed with a male, and not waste energy competing with the males. The second strategy we'll call female.
If the female strategy beats out the hermaphroditic strategy, then we'll wind up with a truly sexual population, where everyone is half as well off as they were under the old hermaphroditic strategy, and the main population has become dependent on the male parasites. (This would be far from the only case where parasitism evolved into symbiosis - and probably wouldn't be the only case where one side of the symbiosis is worse off than they were before they got "helped".)
So, what do you think?
Cheers,
Ben "the parasite" Tilly
I have come to believe that idealism without discipline is a quick road to disaster, while discipline without idealism is pointless. -- Aaron Ward (my brother)
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Post #193,340
2/6/05 11:37:24 PM
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Re: Men are parasites ;-)
I think you have too much time on your hands!
Caenorhabditis elegans is a nematode-earthworms are annelids. Both have to mate to reproduce, although sometimes you will find parthenogenesis occuring in earthworms, but this is not the norm.
To consider your theory, you first have to explain why C.elgens still has males and hermaphrodites in their population. Why do they choose to expend more energy to "find" other hermaphrodite instead of giving up and surrendering to the males? What's in it for them?
Interesting that you define males and females as being in a symbiotic relationship- By definition, symbiosis usually occurs between 2 different species, but I get your point.
I've met a few parasitic men. My ex, for one.
-"I think animal testing is a terrible idea; they get all nervous and give the wrong answers."
"The 2 most common elements in the universe are hydrogen and stupidity."
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Post #193,341
2/7/05 12:37:57 AM
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Why expend more energy? To get more kids.
If a hermaphroditic C. elegans meets another hermaphrodite, both get pregnant and both have kids. It's a 2 for 1 deal! If it meets a male, only one gets pregnant, which is not nearly as good.
Evolutionarily, kids are generally worth some effort.
Conversely a male is only half as well off as a hermaphrodite per encounter. The stable strategy in a mix of hermaphrodites and males is going to be the mix where males average two impregnations for every one that a hermaphrodite gets. What that mix will be depends on a lot of specifics.
A harder question is what the trade-off is between being hermaphroditic and being female. If maintaining the male option takes you very little work and sometimes gives you an extra kid, then there is no reason not to be a hermaphrodite. This would definitely be the case if (as with c. elegans) the evolutionarily stable strategy leaves far less than half the population pure males. But if it takes a lot of energy to maintain the male role and try for those kids in addition to the ones you get as a female, then a straight female strategy could beat the hermaphroditic one.
To figure out when that would happen you'd need to carry out fairly detailed studies to determine what the evolutionarily stable strategy should be. I'll bet that for c. elegans the female strategy loses.
And once you'd passed through an evolutionary bottleneck forcing a species into separate genders, I suspect that re-evolving hermaphroditism could be fairly hard. Which would suggest that you might find species that are purely sexual who'd be better off as hermaphrodites, but you'll not find hermaphroditic species who are better off being sexual.
Cheers,
Ben
I have come to believe that idealism without discipline is a quick road to disaster, while discipline without idealism is pointless. -- Aaron Ward (my brother)
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Post #193,354
2/7/05 3:32:36 AM
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A couple of reasons.
Separate sexes remove the possibility of self fertilization which is likely to be highly degenerative in more complex creatures. This may be the primary reason.
Particularly in humans, a division of labor is necessary because the female is burdened with a child not for just a couple of days or weeks but for years. It'd probably be pretty inconvenient for you and your wife both to be pregnant at the same time, wouldn't it? Some other species also take advantage of partnership and division duties.
[link|http://www.aaxnet.com|AAx]
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Post #193,356
2/7/05 3:55:30 AM
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Second point is pretty much pure circular reasoning, AFAICS.
Da Gryge pontificates: Particularly in humans, a division of labor is necessary because the female is burdened with a child not for just a couple of days or weeks but for years. [Emphasis added - CRC] Uh... But it is "the female" that is burdened with child-rearing for years precisely because that labour is not equitably divided between both parents! Cute language-murder trick there -- calling that lack of a division of labour a "division of labor", using the fact that women are unfairly burdened as a justification that it is somehow "fair" that women are more burdened than men. Not something I would have expected from you, though, Andrew.
[link|mailto:MyUserId@MyISP.CountryCode|Christian R. Conrad]
(I live in Finland, and my e-mail in-box is at the Saunalahti company.)
Your lies are of Microsoftian Scale and boring to boot. Your 'depression' may be the closest you ever come to recognizing truth: you have no 'inferiority complex', you are inferior - and something inside you recognizes this. - [link|http://z.iwethey.org/forums/render/content/show?contentid=71575|Ashton Brown]
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Post #193,360
2/7/05 4:29:04 AM
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We are not talking 'fair' here, we're talking 'survival'.
Neither nature nor evolution is "fair".
The female is not one bit more burdened by the male not having children than she would be if he also got pregnant - only then she wouldn't have an unencumbered partner for support. This still holds true today with an economic emphasis - being a single mom is a lot harder.
Unfortunately, if the species is to continue, somebody gets the job of bearing and feeding the brats.
[link|http://www.aaxnet.com|AAx]
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Post #193,392
2/7/05 11:29:02 AM
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Nature is not PC
If we're meant to have an equitable division of labour, then why is it that only women are naturally capable of feeding infants? (And why are only women sure that kids are really hers?)
Evolution proceeds on the basis of life or death issues. A horribly unfair division of labour where there are lots of kids is (evolutionarily) far preferable to a completely equitable division with 1 kid per couple.
Humans are not as extreme as, say, cats. There dad shows up, the sex really sucks, and mom is stranded with the kittens. That's par for the course for most mammals.
By contrast in humans there is at least a considerable amount of tension about how much work dads are going to do, and dads do wind up doing a significant amount of work. (Though less, in general, than moms do.)
Cheers,
Ben
I have come to believe that idealism without discipline is a quick road to disaster, while discipline without idealism is pointless. -- Aaron Ward (my brother)
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Post #193,386
2/7/05 11:15:06 AM
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Let me address those reasons for strict sexuality
I thought about both of those reasons. And I'm not satisfied with either.
First of all, self-fertilization. It shouldn't be hard to avoid making self-fertilization an option, while still maintaining the option of being a hermaphrodite.
But even so, self-fertilization isn't bad for the reasons that most people think. True, were one of us to self-fertilize, the baby would be likely to have a horrible disease and die. But the problem of self-fertilization resembles inbreeding. As I recall, a population with routine inbreeding is supposed to settle on a steady state with the exact same number of people dying due to genetic disorders as a population with little inbreeding. The genes that would be so lethal for us get bred out of the population. The really bad stuff happens when you take a population without much inbreeding and then inbreed.
Certainly inbreeding is common among great apes. They live in small bands and most matings being within the band, with occasional matings between bands. In fact homo sapiens is believed to have followed a similar pattern for most of its history.
However the more subtle trap is the need to keep genetic diversity up. There is [link|http://www.skyaid.org/Skyaid Org/Medical/scent_of_a_man.htm|evidence] that humans have a mechanism to allow us to select mates whose immune system differs from our own. This gives our offspring good odds of having immune systems that can respond to a wide variety of challenges.
So there is a benefit to avoiding self-fertilization. But I'm dubious that you need to cut the pregnancy rate in 2 to do it.
Now the two parent issue. It is true that humans play a delicate dance around childcare issues. Babies do better with 2 parents. From dad's point of view it is often passable for someone else to raise your kids, but you certainly don't want to raise someone else's. Moms would like to have kids with the best dads possible, but also would really like to have help with childcare (which means convincing someone that this is their kid). And in this set of incentives I've stated the roots of a whole series of conflicting desires and drives in humans.
Similar games are played in many other species, particularly among birds.
However most species of mammals limit parenting to the mother. When you go back to reptiles, amphibians and various kinds of fish, most species have little to no active childcare at all. Yet they mostly use sexual reproduction. I don't see the need to have dual parents as a possible cause for this. (And you can't say, "They evolved it because it would be needed later" - evolution always addresses current issues, not possible ones down the road.)
So I see "avoiding self-fertilization" as dubious but not completely implausible. But I see the need for 2 parents in childcare as being an untenable explanation.
Cheers,
Ben
I have come to believe that idealism without discipline is a quick road to disaster, while discipline without idealism is pointless. -- Aaron Ward (my brother)
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Post #193,492
2/7/05 6:40:18 PM
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well if I were a hermaphrodyte I would never leave the house
but seriously, it wouldnt work because there would still need to be a symbiotic relationship of some sort for late term and 20 days or so after birth when the pregnant parent is not as mobile and is more vunerable. There would have to be a division of work with something. Prior to late term and 20 days after labor a female is as capable in a hunter gatherer society of doing just that. The current design of slot/tab with chemical urgings to continue on seems to be working well.
regards,
daemon
I love her dearly, far beyond any creature I've ever known, and I can prove it, for never once in almost seventy years of married life have I taken her by the throat. Mind you, it's been a near thing once or twice.
George Macdonald Frasier
Clearwater highschool marching band [link|http://www.chstornadoband.org/|http://www.chstornadoband.org/]
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Post #193,493
2/7/05 6:48:57 PM
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Don't confuse "hermaphroditic" with "flexible"...
Regards,
-scott anderson
"Welcome to Rivendell, Mr. Anderson..."
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Post #193,500
2/7/05 8:15:47 PM
2/7/05 8:17:54 PM
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It works for nematodes
And just try to get a bull sea lion to do anything other than sleep or breed.
My point being that specifics of how things work for homo sapiens don't necessarily apply to the animal kingdom as a whole.
Cheers,
Ben
I have come to believe that idealism without discipline is a quick road to disaster, while discipline without idealism is pointless. -- Aaron Ward (my brother)
Edited by ben_tilly
Feb. 7, 2005, 08:17:54 PM EST
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Post #193,503
2/7/05 8:36:32 PM
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Y'all take all the mystery out of procreation
Where's DRL when you need him to lively up a discussion on the difference in the sexes? :-)
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Post #193,504
2/7/05 8:38:19 PM
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Out drinking? Reading Jung? Casting a horoscope?
I have come to believe that idealism without discipline is a quick road to disaster, while discipline without idealism is pointless. -- Aaron Ward (my brother)
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Post #193,555
2/8/05 9:41:10 AM
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OT: Where TH is Ross anyway?
bcnu,
Mikem
Eine Leute. Eine Welt. Ein F\ufffdhrer.
(Just trying to be accepted in the New America)
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Post #193,558
2/8/05 9:59:26 AM
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Re: OT: Where TH is Ross anyway?
[link|/forums/render/content/show?contentid=184215|Read all about it]
-YendorMike
"They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety."
- Benjamin Franklin, 1759 Historical Review of Pennsylvania
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Post #193,564
2/8/05 10:05:38 AM
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Ah. Thanks. Missed that.
bcnu,
Mikem
Eine Leute. Eine Welt. Ein F\ufffdhrer.
(Just trying to be accepted in the New America)
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Post #193,561
2/8/05 10:00:09 AM
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Atlanta, IIRC. ... Oh, you mean. Well, he ran away. :-(
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Post #193,570
2/8/05 10:23:20 AM
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I agree
Ross would definitely add another dimension to this convo. I hope he comes back soon.
Brenda
Nightowl >8#
"The people of the world having once been deceived, suspect deceit in truth itself." -- Hitopadesa 600?-1100? AD, Sanskrit Fable From Panchatantr
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Post #193,506
2/7/05 9:05:16 PM
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dont have to try, they fight real well (bull sealions)
I think what we should be looking at is hominids in general and humans in particular. There has been many methods of running a herd of humans, most depend on the geographical complexity of the are they live in.
regards,
daemon
I love her dearly, far beyond any creature I've ever known, and I can prove it, for never once in almost seventy years of married life have I taken her by the throat. Mind you, it's been a near thing once or twice.
George Macdonald Frasier
Clearwater highschool marching band [link|http://www.chstornadoband.org/|http://www.chstornadoband.org/]
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Post #193,391
2/7/05 11:24:01 AM
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Exactly
-"I think animal testing is a terrible idea; they get all nervous and give the wrong answers."
"The 2 most common elements in the universe are hydrogen and stupidity."
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Post #193,346
2/7/05 1:44:47 AM
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Re: He has past cause...
An ex-member was very fond of creating lots of accounts, trying to get people to believe they were real, and then having them argue with each other. This got old. Fast. Particularly the bit where the alter-egos persecuted the original. But you're obviously not him. Too verbally adept. And that is a huge relief, too. :) Welcome, Bionerd, I'm Owl. I'm also a female. ;) Brenda
"The people of the world having once been deceived, suspect deceit in truth itself." -- Hitopadesa 600?-1100? AD, Sanskrit Fable From Panchatantr
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