tag:blogger.com,1999:blog-1461700565722278823.post8144154522606922904..comments2024-02-27T14:44:07.868+01:00Comments on Greedy goblin: LFG biologistGevlonhttp://www.blogger.com/profile/07072766785893313616noreply@blogger.comBlogger33125tag:blogger.com,1999:blog-1461700565722278823.post-7588015868193567962010-09-29T04:38:01.140+02:002010-09-29T04:38:01.140+02:00Had read this before, but after thinking about it ...Had read this before, but after thinking about it there is an argument which is similar to what Phaelia posted. Keep in mind:<br />1) even tiny animals living in the ocean feeding off of whale bones usually have sexes<br />2) behavior does not always have an effect on choice, since (again for ocean animals, etc.) the reproductive cells are released directly into the water sometimes<br />3) sometimes the large female spider eats the smaller male spiders of a species, etc.<br /><br />So similar to what Phaelia said, it might be the result of specialization [slight penalty when not specialized adds up over evolutionary time], and also speed of propagation or loss of specific traits, due to the differences of behavior and effect of genes. (Such as the slightly higher variance of performance of males described in another article here)Taemojitsuhttp://daughterofankh.blogspot.com/noreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-31471993227040694992009-07-26T14:19:11.403+02:002009-07-26T14:19:11.403+02:00The more intellectual creature is, the more time i...The more intellectual creature is, the more time it needs to grow up and be independent. You can see a lot of examples looking at animals of all species. So it takes more and more time just to brood a child, and eventually comes to a situation where pregnant creature or creature with children can't leave without assistance of others. So we need some to brood, and some to gather food etc. And while hermaphroditic creature has no reason to feed and guard children of other hermaphroditic creature, male has very strong reasons to feed and guard females and his children, as it is his children too, and otherwise he can't have any. So by having 2 sexes we have a possibility to extend brood and growth time.<br />Actually we see hermaphroditic forms only on stages of evolution before livebearings.Leehohttps://www.blogger.com/profile/07438956683794597730noreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-40719436625119885972009-01-29T19:49:00.000+01:002009-01-29T19:49:00.000+01:00@phaelia: I'm at home and could access the whole a...@phaelia: I'm at home and could access the whole article only from the university, now I just see the abstract. Could you mail the pdf to me?Gevlonhttps://www.blogger.com/profile/07072766785893313616noreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-82578248275812414832009-01-29T19:41:00.000+01:002009-01-29T19:41:00.000+01:00I found a paper very relevant to this discussion f...I found a paper very relevant to this discussion from Eric Charnov and John Maynard Smith, two of the biggest names in the business when it comes to evolutionary ecology modelling. I did not review their math, but they concluded that hermaphroditisim is only stable with low mobility (plants or low mobility animals), when the resources needed for female reproduction are different than male reproduction (seasonally pollenating plants), and when males and females have to expend roughly the same same amount of resources for reproduction (insect-pollinating plants). Otherwise, the male/female system is stable and hermaphrodites cannot invade.<BR/><BR/>http://www.nature.com/nature/journal/v263/n5573/pdf/263125a0.pdfLoni Huffhttps://www.blogger.com/profile/01133567916019535449noreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-81825678945685443782009-01-29T19:39:00.000+01:002009-01-29T19:39:00.000+01:00@hermaphrodites do exist, like 99% of the plants. ...@hermaphrodites do exist, like 99% of the plants. So I wouldn't call them unstable. You could claim that hermaphroditism is *so* unstable that it cannot survive, but it's obviously not true as they do exist.<BR/><BR/>Even if hermaphroditism would be unstable, the existing hermaphrodites should rule their niche until they also split into sexes.<BR/><BR/>The other problem is the existence of females. Males van be cheater hermaphrodites, but why would any hermaphrodite choose to be female? By doing so she gives up the chance to be father of *some* offspring, even if most of her offspring come from female role. But a few is bigger than zero.<BR/><BR/>And finally: there are split-sex and hermaphroditic races. Why there is no intermediates who are just in the middle of transition? <BR/><BR/>They should have males and hermaphrodites who are doing some kind of desperate defense (egg-trading, long mating) against the invading males. You can find some 100K of hermaphroditic and millions of split-sex races but *no one* in the middle of this important evolutionary step? Why?Gevlonhttps://www.blogger.com/profile/07072766785893313616noreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-52588053148813983452009-01-29T18:48:00.000+01:002009-01-29T18:48:00.000+01:00@Gevlon: I believe the infidelity birth rates amon...@Gevlon: I believe the infidelity birth rates among birds that "mate for life" is something like 20%, which demonstrates just how difficult it is to maintain "hermaphroditic sex roles" in larger animals. I also imagine it is very easy to mutate into a psuedo-male; practically any mutation that would break or even slow down the female reproductive system should do the trick. So any population of hermaphrodites should have plenty of "males" to pick from, and the behavior should spread rapidly if it's favored within the group. I don't think a male/female group would have to compete with a hermaphroditic group of the same niche because the hermaphroditic group is inherently unstable. <BR/><BR/>Also, there is more to fitness than maximizing reproductive rate, so I do not think the evolution of 2-sexes would cause a 50% fitness reduction to the group. Certainly, reproductive rate matters for invasive species or colonization events, but most of the time the size of the group is relatively stable. Looking at brood size adjustment in birds, females in many species clearly have the capacity to ramp up their reproductive efforts in response to additional resources, so the fitness cost of males to the group could be quite minimal.Loni Huffhttps://www.blogger.com/profile/01133567916019535449noreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-18070965706287915542009-01-29T18:21:00.000+01:002009-01-29T18:21:00.000+01:00@Phaelia: Group selection is a more or less outdat...@Phaelia: Group selection is a more or less outdated idea and I don't believe in it either. I just say that the individual animal is competing not only with other members of his species but with members of other specieses.<BR/><BR/>If males are just "parasites", who forced the hermaphrodites into costly female roles, than the average member of this species has half of the fitness of a member of a hermaphroditic species (of similar niche). So they would die out.<BR/><BR/>BTW hermaphrodites could defend themselves against the cheating of males by other mechanisms like "marriage" (several birds choose mate for life), the cheater can cheat once but never again.<BR/><BR/>They could also try to actively punish cheating by attacking the cheater (female locusts attack their mate if he makes the "LFG female" noise).<BR/><BR/>So I think the "fixation of error" or "male = cheater hermaphrodite" is not convincing.Gevlonhttps://www.blogger.com/profile/07072766785893313616noreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-29593427446089368842009-01-29T18:02:00.000+01:002009-01-29T18:02:00.000+01:00@Gevlon: Egg trading as an anti-cheating mechanism...@Gevlon: Egg trading as an anti-cheating mechanism can only be effective when most of the female effort is spent in the production of eggs and not gestation, so it would only work for small organisms. As far as the species with the males dying out is concerned, well I personally don't believe in group selection but since its a matter of faith you are of course free to have your own beliefs. :-)Loni Huffhttps://www.blogger.com/profile/01133567916019535449noreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-69974482774069331042009-01-29T07:47:00.000+01:002009-01-29T07:47:00.000+01:00@Phaelia: Several hermaphrodite species have "egg ...@Phaelia: Several hermaphrodite species have "egg trading" mechanisms, exactly to prevent such cheating. The first (usually the weaker or otherwise less attractive) hermaphrodite release a *few* eggs (female role) and the other one release sperm (male role). Than the second hermaphrodite takes the female role. If it refuses to, the first walks away. So the *existing* hermaphrodites have defense mechanism against being forced to take the more costly female role. They often has long dating mechanism to make sure that the other is not a cheater (long dating is too costly to do it for only the first turn). So they are not so naive as you think.<BR/><BR/>On the top of that: if the males were just cheaters, than the fitness of whole species would fall below the species of (yet) non-cheating hermaphrodites and die out. While male-cheating mutations would spread quickly in a population, soon the population itself would die out.Gevlonhttps://www.blogger.com/profile/07072766785893313616noreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-3357272367730894442009-01-28T23:56:00.000+01:002009-01-28T23:56:00.000+01:00@Gevlon: I think you are hypothesizing about herma...@Gevlon: I think you are hypothesizing about hermaphrodites that are incapable of self-breeding, or at least that only do so very rarely. It's true that such a species would have the advantages of 2-sexes without the disadvantages. However, this system has a major evolutionary stability problem: if it's advantageous to produce more males when there are fewer males than females, then it's certainly advantageous to produce males when there are no males in the population at all!<BR/><BR/>Once you have a population of naïve females doing all the work, a cheater can show up that refuses to play nice and instead just focuses on spreading its seed. Once this first "male" is born, its genes will spread rapidly through the population until they reach 50/50 or so. After that, the gene frequencies might bounce around for awhile until the "male" gene gets accidentally copied onto its own chromosome, or until some developmental mechanism is established to "set" the sexual role of the hermaphrodite early in life, etc.<BR/><BR/>Meanwhile, the hermaphrodites that are playing by the rules are forced into the female role, because they cannot compete with the gamete production/dissemination males, so they are better off specializing as well.Loni Huffhttps://www.blogger.com/profile/01133567916019535449noreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-18150220567628151402009-01-28T23:30:00.000+01:002009-01-28T23:30:00.000+01:00maby i wote in a manner that made you think that i...maby i wote in a manner that made you think that i think sexs came first, but i did not mean to say that. the point i was attempting to make is that its 2 different methods, each a working method that leads to the same end, reproduction. both are successful, and there for survive.Unknownhttps://www.blogger.com/profile/14670432179828878508noreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-33003978807292215492009-01-28T21:45:00.000+01:002009-01-28T21:45:00.000+01:00@phaelia: most text mentioning "sexual" reproducti...@phaelia: most text mentioning "sexual" reproduction actually talking about "meiotic" or "via gametes" reproduction. However this does not need "sexes". The sweeping of disadvantageous mutations and the quick spread of advantageous ones does *not* need sexes as meiotic (not self-fertilizing) hermaphrodites can enjoy it. The question is about the two sexes. It basically have three explanations in the literature:<BR/><BR/>* fixation of an error (ridicolous)<BR/>* runaway sexual selection (actually not, since hermaphrodites could also "run away" but they never did)<BR/>* handicap principle<BR/><BR/>If you know of others I would appreciate them.<BR/><BR/><BR/>However a very brief version of my calculation (I have normal extensive ones):<BR/>Imagine that there are 6 hermaphroditic giraffes, 10,10,11,11 and 12,12 feet tall. Due to selection, only 4 reaches maturity, the 11,11,12,12 feet tall ones. The average height of the children will be 11.5 feet, so in a generation they win 0.5 feet.<BR/><BR/>If we have 3 female (10,11,12) and 3 male giraffes (10,11,12), 4 reaches maturity, we get the same result, except the females have to carry 2x more offspring to match the hermaphrodites.<BR/><BR/>However if we place a handicap to the males, decreasing their survival rate, we get the two mature female giraffes (11 and 12) and ONE surviving male (12). Since both females have offspring from this one male, their children will be 11.5 and 12 feet tall, making the average height of the next generation 11.75 (instead of 11.5)<BR/><BR/>Of course the real case with gaussian survival probabilities is much more complicated, but the result is the same.<BR/><BR/>The handicap is enforced by the females. If a mutant male is not handicapped, his survival rate increases but the females reject him so he cannot reproduce. The females have selfish interest is choosing a handicapped male as it has proven (by survival against the handicap) that it has several benefical qualities.Gevlonhttps://www.blogger.com/profile/07072766785893313616noreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-71112076486177490612009-01-28T20:57:00.000+01:002009-01-28T20:57:00.000+01:00@Artorin: It's true that right now we are compensa...@Artorin: It's true that right now we are compensating for poor eyesight with glasses, but why would we continue to do so when glasses are considered unattractive? If we can eliminate it genetically, we will probably do so since people would rather not need to wear glasses or for their children to have to wear them (children are typically not candidates for Lasik corrective surgery). The same is true with artificial heart valves. At some point it will be easier and less expensive to eliminate or reduce the risk factors of needing them than performing the costly and dangerous surgery to install them.<BR/><BR/>Changes like the addition or substitution of mechanical limbs will be much more difficult to "sell" to the population because of the perception that such things are "weird" and therefore less sexually attractive. A math chip in your brain, however, would probably do very well and is likely something we can't achieve genetically so the actual world we end up with will likely be a mixture of both genetic and technological enhancement, with technological changes limited primarily by what we as a society perceive as sexually attractive.<BR/><BR/>@Gevlon: We have had a lot of interesting conversation that is easy to get lost in, so I am hopefully going to come back to the central idea: that the handicap principle is behind the evolution of sex. There are plenty of examples of "runaway sexual selection" such as the classic Peacock's tail, but to my knowledge they are in species where sex has long been established, and for every solid example of the evolution of costly signaling, there are hundreds of thousands if not millions of examples of species with very similar males and females (limited sexual dimorphism).<BR/><BR/>Further, while costly signaling raises the fitness of the individual, the spread of the behavior lowers the fitness of the population relative to other species, so it does not seem likely that it would be a major factor in the evolution of sex, or even come into play until long after the sex roles have been established.<BR/><BR/>Sex clearly has several disadvantages. As you have pointed out, the biggest disadvantage is in the rate of reproduction. In a species where rapid reproduction matters much more than anything else, the disadvantages of sex may well outweigh the advantages (and is part of the reason that bacteria are so successful). However, sex allows disadvantageous mutations to quickly and efficiently be swept from the population while allowing advantageous mutations to quickly spread through the population. Sexual reproduction will likely evolve wherever it is important to be able rapildy adapting to new and/or changing environments. Though not immediately obvious, by the same logic sexual reproduction should be favored for populations with a small number of individuals since they have a smaller pool of advantageous mutations to pull from.Loni Huffhttps://www.blogger.com/profile/01133567916019535449noreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-68567907671219345422009-01-28T20:38:00.000+01:002009-01-28T20:38:00.000+01:00Maybe you should look to the Daphnia to gain an un...Maybe you should look to the Daphnia to gain an understanding of sexual/asexual reproduction. Hermaphrodites aside, this model species may provide insight into the benefits/motivations? of either form of reproduction.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-51638870923007364352009-01-28T19:22:00.000+01:002009-01-28T19:22:00.000+01:00@Phaelia: The handicap principle need sexual *role...@Phaelia: The handicap principle need sexual *roles* and not biological split-sex. So Serraninae can have the handicap principle. Of course its not proof of having it. It just says that it is possible. The exact calculations, (that were not published here as being more complicated than a DPS chart) are the proof. I gladly send you tomorrow if you are interested (I need some time to translate the text)<BR/><BR/>The 1 male 100 female means 1 alive and reproductive male and not male Zygote. Several species, like seals have worse ratio. 1 male haremlord can have 2-300 females (non-haremlord males do not count as not able to reproduce).<BR/><BR/>I don't argue with 50-50 (or slightly more) male zygote is evolutionary stable strategyGevlonhttps://www.blogger.com/profile/07072766785893313616noreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-86574888668049547572009-01-28T19:20:00.000+01:002009-01-28T19:20:00.000+01:00@Phae: Very interesting but I would argue that our...@Phae: Very interesting but I would argue that our technology has made up for our shortcomings and even in genetic engineering it wouldn't be as much as human evolution as it would be techonological. In another bout of Sci Fi 2001 space oddessy series talks about how eventually people evolve sort of into technology essentially ultimately becoming beings of energy with limitless knowledge. Our bodies become more frail as our minds become stronger eventually exceeding mortal bounds. <BR/><BR/>Be it mechanical limbs, brail computers, artificial heart valves or even anti depression medications we are compensating for our mutations rather then eliminating them. Glasses allowed people with poor vision to live longer more productive lives when before they would have been undesireable. So we don't create environemnts that promote poor eye sight but we do compensate for it therefore allowing those genes to become more widespread.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-78341372457961046952009-01-28T19:08:00.000+01:002009-01-28T19:08:00.000+01:00@Gevlon: Your description of Serraninae does not d...@Gevlon: Your description of Serraninae does not describe the handicap principle but rather describes a starting stage in the evolution of sex. That is a very transient stage, and it's not clear that any sort of costly signaling could evolve when the sexes are so "fluid."<BR/><BR/>"Short supply" is never expressed in terms of sperm count vs. egg count. Men produce trillions of sperm over the course of their lives, but we don't use that number to determine population or who is in short supply. Population is always measured as % male vs. % female, and that ratio is generally close to 50/50 with slightly more men born than women but more women living to reproductive age than men.<BR/><BR/>In your example, if there is one male born for every 100 females, then a gene that makes it slightly more likely to produce a male would be amazingly advantageous and spread very rapidly through the population, because a male has 100x the fitness of a female. This rapid spread would very quickly bring the population close to 50/50.Loni Huffhttps://www.blogger.com/profile/01133567916019535449noreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-14978157383403829872009-01-28T18:55:00.000+01:002009-01-28T18:55:00.000+01:00@Artorin: Just because we are powerful enough to c...@Artorin: Just because we are powerful enough to create our own environment does not mean we are no longer bound by selection. Though I would still consider it artificial selection, it's very different than breeding for a cow that produces more milk. To extend the eyesight example, we have not intentionally created environments that allow poor eyesight to spread. We are still very much bounded by evolution, but many of the selection pressures we face now are man-made. However, if genetic engineering in humans ever becomes a reality, then we may truly start "evolving ourselves."<BR/><BR/>We're already seeing the beginnings of this with pre-natal screening for genetic disorders. Eventually, this will extend to engineering for positive mutations like those that give boosts to intelligence, though this type of service is likely to restricted initially to those who can afford it (at least within capitalist societies).<BR/><BR/>At some point, however, the first societies will make the leap of providing widespread genetic planning for members of their society that could not otherwise afford it on their own. Those societies are likely to quickly out-compete those that resist or restrict this type of family planning (for ethical reasons or otherwise), increasing the pressure on other 1st-world countries to follow suit.<BR/><BR/>I think the world depicted in the movie Gattaca is extremely close to becoming a reality.Loni Huffhttps://www.blogger.com/profile/01133567916019535449noreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-59848939024794543062009-01-28T18:54:00.000+01:002009-01-28T18:54:00.000+01:00@Captain The First: that's very interesting, could...@Captain The First: that's very interesting, could you give the reference of that article so I can seek it in the library?<BR/><BR/>@Artorin: Phaelia is right about asthma and such. Several bad traits shown after reproduction, or not shown at all due to recessive gene.<BR/><BR/>@Phaelia: at first warm welcome here, yours were the first blog I read. And sorry, but wrong: the separate sexes were not needed for handicap principle. Several existing hermaphrodites, like the Serraninae (fish) are taking male or female roles exclusively. The big fish are "males", fighting with each other for the harem of small "female" fish. But they are NOT males and females but fully functional hermaphrodites who "choose" to act like males and females. This could be the start point of separation of sexes. The roles already existed when the only-male or only-female mutant was born.<BR/><BR/>And females are ALWAYS in shorter supply. If there is one male and 100 female, who is in short supply? The females since the male still have unused sperms while all the females are pregnant.<BR/><BR/>@Joel: already read it, but thanks.Gevlonhttps://www.blogger.com/profile/07072766785893313616noreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-79090906181774768882009-01-28T18:35:00.000+01:002009-01-28T18:35:00.000+01:00So does that mean that evolution has an end? If hu...So does that mean that evolution has an end? If humans are powerfull enough to essentially create our own environment does that mean that we are no longer bound by natural selection and evolution?<BR/><BR/>Is that the natural progression of worlds? Evolution occurs until a species can overcome and create its own environment. Natural selection becomes artifical selection?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-22572605161260111282009-01-28T18:23:00.000+01:002009-01-28T18:23:00.000+01:00@Artorin: Humans today are no more "naturally sele...@Artorin: Humans today are no more "naturally selected" than the plants or animals we have domesticated. We are becoming an artificially selected species, as we are creating our own environments with their own selective landscapes. If the technology we develop eliminates the fitness disadvantage for poor eyesight, you can be sure that poor eyesight will spread, but that is no cause for concern since the only reason it can spread is that it is causing no major harm.Loni Huffhttps://www.blogger.com/profile/01133567916019535449noreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-70133897758310849382009-01-28T17:57:00.000+01:002009-01-28T17:57:00.000+01:00See but thats my point Phae. I understand how they...See but thats my point Phae. I understand how they got passed on but it seems to conflict with natural selection and evolution. While some of the things I mentioned don't appear until later in life other things such as poor vision can develop very early in life yet a significantly high portion of the population suffers from this. <BR/><BR/>I know technology has a big involvement looking at how the life span of people has doubled in the last 100 years do to this. We aren't living longer because our bodies evolved in a way that makes our lives longer, we live longer because our techonology allows us to. <BR/><BR/>Poor vision was corrected with the use of glasses and even to the point now where laser surgery can all but eliminate poor vision. Yet the genes that cause it will still be there and only continue to spread. I can see a few hundred years down the road most people being born blind but due to surgery performed at birth flawed genetics will continue to survive.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-58311198688446345902009-01-28T17:49:00.000+01:002009-01-28T17:49:00.000+01:00Here's another way to think about it. Any time a n...Here's another way to think about it. Any time a new mutation shows up in a single individual that provides a fitness advantage, the individuals in the population that are genetically predispositioned to outbreed more often have an long-term reproductive advantage because they are more likely to pick up the new mutation through outbreeding. If there are enough advantageous genetic variants floating around in the population, then it will be advantageous to outbreed every generation.<BR/><BR/>We are just beginning to get a handle on the frequency of new advantageous mutations, but in humans there are hundreds of genes that have been influenced by strong positive selection in the last 40,000 years or so. Even with just a handful of moderately advantageous variants floating around in the population, hermaphrodites would not have a chance.Loni Huffhttps://www.blogger.com/profile/01133567916019535449noreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-53267237743036212802009-01-28T17:42:00.000+01:002009-01-28T17:42:00.000+01:00This articleIs There Anything Good About Men? And ...This article<BR/><A HREF="http://tierneylab.blogs.nytimes.com/2007/08/20/is-there-anything-good-about-men-and-other-tricky-questions/" REL="nofollow"><BR/>Is There Anything Good About Men? And Other Tricky Questions</A> might be of interest to you as it discusses this topic. Have fun!Joelhttps://www.blogger.com/profile/05577775813360031108noreply@blogger.comtag:blogger.com,1999:blog-1461700565722278823.post-64826115998055415682009-01-28T17:39:00.000+01:002009-01-28T17:39:00.000+01:00You appear to be arguing that the handicap princip...You appear to be arguing that the handicap principle is the reason for sexes to have evolved. This cannot be, however, since the handicap principle requires established sexes to begin with. If the males' purpose is to "suck", then surely the hermaphrodites would easily out-compete their 2-sex cousins.<BR/><BR/>The one sex in shorter supply doesn't make a lot of sense either. Males are prone to higher risk behaviors and will therefore always be in shorter supply. That has no fitness consequence on the population, however.<BR/><BR/>One problem with hermaphrodites, evolutionarily speaking, is that they will often self-breed rather than outbreed. The evolution of sexes forces them to outbreed every generation. There are lizards in the U.S. of the same species; in some geographic regions, they self-breed and in others they outbreed, and the trigger seems to be climatic stability. In other words, if the environment changes too frequently for hermaphrodites to keep up, 2-sex species will outcompete.<BR/><BR/>@Artorin: Many of the handicaps you describe would not necessarily have interfered with sexual reproduction (high blood pressure is often only a problem at an age where you are likely to have had children already). Asthma (and other allergies) are currently thought to be the body's response to a "bored" immune-system. Sort of a "what else do I have to do now that there's no mammoth poop around?" And many diseases have been found to be linked to other, seemingly-unrelated advantages. For instance, one of the genes associated with breast cancer is thought also to give a boost to intelligence. Many generations of closed-society breeding has lead Ashkenazi (European) Jews to have a number of genetic disorders that are also strongly associated with an increase in intelligence, so it's easy to see how these disadvantageous disorders might have survived.Loni Huffhttps://www.blogger.com/profile/01133567916019535449noreply@blogger.com