|
|
|
|
|
| Evolutionary question?
Posted: 1/23/2008 10:55:56 PM | I know "survival of the fittest" is the explanation for evolution, and that "random" gene mutations are credited with how species evolve, but am I the only one that finds that a bit weak as an explanation? It would seem that a specie's chances of getting a beneficial gene mutation would be less likely than winning the lottery 10 times in a row. It smacks of happy coincidence. I know creationism sounds like a fairy tale, but evolution sounds like half an explanation.
It would seem that technological evolution would be a direct result of biological evolution. Human evolution seems to have taken the "big brain, wimpy body" route, (coincidentally, of course) so technology is a direct result of that. Maybe your question shouldn't be about which sex, but which group of humans, i.e., ethnic, religious, societal, nationality, etc., is now shaping our evolution. Just a thought. | |
|
| Evolutionary question?
Posted: 1/24/2008 2:17:57 AM | > It would seem that a specie's chances of getting a beneficial gene mutation
> would be less likely than winning the lottery 10 times in a row.
Yes, it's true that most mutations are not beneficial. But then someone does win the lottery almost every time they have a drawing. Having a positive mutation is like that. It's its very rarity which makes it so valuable. | |
|
| Evolutionary question?
Posted: 1/24/2008 9:15:52 AM | Smartblonde...
You have to think of evolution in terms of millions of years. It is a long, long time for gene mutations to take place and for the more successful mutations to prosper. A successful gene mutation allows for the host (be it human, animal or plant) to thrive and generate more offspring that carries the mutation. There were probably other gene mutations that didn't serve any purpose towards thriving in the environment and consequently the host died out and that was the end of the mutation.
In regards to technology, you are making the assumption that technology only covers the twentieth century. Any technological increase in weapons, hunting styles, fire making, metal making allowed for more 'primitive' man to move ahead and be successful in gathering food and enhance his/her chances of survival. These early humans were most certainly not 'wimpy'. | |
|
| Evolutionary question?
Posted: 1/24/2008 11:19:56 AM | Altho we do shape our own evolution, our environment is just as important if not more so in shaping it, at least in the past. For instance, if males and females find it difficult to locate each other, then parthenogenesis will be favored regardless of how horny a species is. Another example is the loss of pigmentation in animals that live out of the light in caves, the deep sea, or the bodies of other organisms.
I suspect that these days, however, human evolution is shaped more by what we want to do better. For instance, speech as we know it evolved physically (vocal cords, larynx, brain vocalization center) because early hominins found that their voices could be used for more than just vocalizations like those of wildcats and chimps, and because the success of early proto-languages enhanced survival and reproductive success.
We take care of our weak and our old, as did Neandertals and, probably, Homo habilis. Review the grandmother hypothesis, wherein non-reproductive females contribute to the survival of her daughter's children and the longevity of her daughters.
It is well-known that people who grow up not knowing more than a few numbers (say, numbers 1, 2 and 3) cannot learn much more than that about numbers because their brains didn't get wired for numbers during their formative years. Too, "wolf-children" and closet-raised people are forever retarded for the same reason. It stands to reason that teaching very young children as much as possible about music, math and physics causes increased subject-specific brain development and thus might enable them to learn more than their ancestors ever were capable of. If a mutation comes along that allows for even better wiring, that early-on education will be even more powerful a driver of evolving higher intelligence.
Caveat: My knowledge of evolution is based on 1960s college (I'm a wildlifer), ongoing Science mag (AAAS) articles, and an occasional seminar. I appreciate the contributions of more recent students like Humanespresso.
BTW, parasites infest the strong and healthy, not just the weak. I got 'em by eating dirt as a kid - ask your mom, she just might tell you that you did, too! My first job out of college included doing stomach analyses of numerous species of wildlife (snakes, frogs, turtles, birds, mammals), and almost every one of them had intestinal roundworms, many had liver flukes, and I saw plenty of hookworms, too. Interestingly, the parasites were more abundant during the height of summer, when wildlife tends to feed the most, whereas parasite loading was lowest during winter.
It's good to see so many people here discussing evolution. The Am Assoc for the Advancement of Science (AAAS) conducted a poll not long ago and found that 60% of Americans do NOT believe in evolution. No wonder so many right wing-nuts get elected President! Please, in the future, to help counteract this atrocious situation, refer to the subject as "evolutionary science" rather than "evolutionary theory." Evolution is a fact, not a theory. There are various hypotheses and theories regarding nuances of evolution, but the overall concept is a fact. Don't give the **stards even a fingerhold.
Off my soapbox. For now. LOL | |
|
| Evolutionary question?
Posted: 1/24/2008 3:29:13 PM | Panagonia -
I do understand that over millions of years, some good mutations are bound to occur. What I do find difficult to believe is that they would be random. I don't know what the explanation is, but I don't think evolution theory accounts for that fact that so many of these mutations seem to have purpose. Please feel free to correct me if I am wrong on this one.
As far as technology is concerned, I was including all of our advances, from primitive man to the present. I think you will agree, humans today are probably not as strong as primitive man (maybe?) but compared to other mammals of similar size, we are not going to win any strength contests or physical endurance contests. We also take longer to physically mature than just about any other animal on the planet. Probably due to the fact that so much energy is diverted from physical growth to brain development. This leaves us physically vulnerable for a long time in our development. | |
|
| Evolutionary question?
Posted: 1/24/2008 4:04:08 PM |
I do understand that over millions of years, some good mutations are bound to occur. What I do find difficult to believe is that they would be random. I don't know what the explanation is, but I don't think evolution theory accounts for that fact that so many of these mutations seem to have purpose. Please feel free to correct me if I am wrong on this one.
Genetic mutations ARE random. It's just that the negative mutations generally die out quite early, or are bred out before they're obvious within the population. What appears as being 'positive' is also contextual. Sometimes an animal with thicker skin would be better off e.g. something living amongst thorny acacias etc. Other times, it's a hindrance, when the animal needs to be able to run quickly for example.
In the end, it's much like having a million different jellybean colours and your current place in the eco-system has a preference for say, red. Therefore, the 'red' genotype and thus phenotype are ALLOWED to survive and perpetuate themselves. Later on the colour preference may indeed change, in which case, you'll just have to wait until a particular genetic mutation occurs that may allow your species to cope BETTER. It's only a matter of time afterall. | |
|
| Evolutionary question?
Posted: 1/24/2008 5:02:59 PM | Smartblonde:
The only purpose...was that they allowed the host to thrive in the environment. Random mutation, random chance that allowed a species to adapt and better survive. That is the purpose of life - survive and live. The only purpose, really. Everything else is just icing on the cake so to speak.
I would disagree with one part of what you are saying: humans today are probably more developed due to better access to nutrition and less physical stressors. (This doesn't include all the sedentary folks out there). :)
Whales take a tremendous amount of time to mature to sexual maturity as well...for example, the female sperm whale can take up to nine years to reach sexual maturity while the males mature at approximately 18-20 years. The life expectancy is 70 years. The gestation period is around a year and a half...
"Primitive" man/woman were lucky or fortunate to live to their forties, let alone see their thirties. When you factor in sexual maturity for girls/boys to start at around 12(could be younger or older) and they probably did have children at that age, then you realize that we don't really take a long time to develop (sorry, run on sentence there). Childhood lasting into your late teens, early twenties (and for some: forever!) is a recent phenomenon.
There is the correlation as well with smaller number of offspring in ratio with a lower mortality rate. Where there is a high mortality rate, the more offspring. Natures way of ensuring genes are passed down from generation to generation. | |
|
| Evolutionary question?
Posted: 1/25/2008 10:48:18 AM | Panagonia -
I am not sure if my communication skills are lacking, or if you are intentionally misunderstanding what I write. Yes, sperm whales take a long time to reach sexual maturity. (although, if you read my post, you will see that I said physical maturity) But, they don't take longer than us. Females mature between 7 and 13 years, and males reach sexual maturity at about 10 years old. (although they save themselves until they are in their 20s before engaging in sexual conduct) Plus, they weigh about one ton when born, and have only 2 predators to worry about - orcas and humans.
If you will refer to my previous post, you will see that I was comparing modern humans to other mammals of SIMILAR size. | |
|
| Evolutionary question?
Posted: 1/25/2008 11:52:06 AM | | I dont, know I was not their when it happened, how could I know. | |
|
| Evolutionary question?
Posted: 1/26/2008 12:07:16 AM | | survival of the fittest is shaped by environmental conditions. the will and determination to procreate at all costs is survival of the fittest. the most effective carry their genes on to the next gen | |
|
| Evolutionary question?
Posted: 1/26/2008 8:18:14 AM | Smartblonde...
Haven't forgotten you. Am reading about the human slow growth rates in the context of environment and benefits of having dependent offspring in terms of energy demands placed on providers. Might want to read this:
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1560216 | |
|
| Evolutionary question?
Posted: 1/28/2008 6:02:35 PM | The male Y chromosome is diminishing. Hell, given enough time, it will be nothing more than genetic junk.
So that said, it would appear that Women are the dominate sex after all as Men look set to "die out". But don't sweat it guys... In the womb, the default position of the foetus is female... So yeah, we were ALL female once.
I'm assuming Mother Nature will have some sort of trick up her sleeve to ensure that we can still reproduce naturally... But then again, maybe our scientific knowledge would have advanced so much by then that we wouldn't need Her help anyway.
Anyway... Enjoy your manhood’s for as long as you can guys  | |
|
| Evolutionary question?
Posted: 1/28/2008 6:33:32 PM | Two Hawks takes the Talking Stick"
Msg 5:
There is no survival of the fittest. Humans evolved from the weakest apes that were forced out of the trees in a struggle for food.
WRONG! Man as we know him is NOT descended from primates!
Two Hawks passes the Talking Stick | |
|
| Evolutionary question?
Posted: 1/28/2008 6:35:31 PM |
I do understand that over millions of years, some good mutations are bound to occur. What I do find difficult to believe is that they would be random. I don't know what the explanation is, but I don't think evolution theory accounts for that fact that so many of these mutations seem to have purpose. Please feel free to correct me if I am wrong on this one.
None of them 'have a purpose.' Some turn out to be usefull, some turn out to be harmfull, and the vast majority make no difference whatsoever.
We only think they have a purpose (suggesting to us that they were preordained) because the ones that accidentally turned out to be useful tended to get passed on. The rest usually disappear within a generation or two. So nearly everything that sticks around 'has a purpose.' | |
|
| Evolutionary question?
Posted: 1/29/2008 6:50:36 PM |
The male Y chromosome is diminishing. Hell, given enough time, it will be nothing more than genetic junk.
So that said, it would appear that Women are the dominate sex after all as Men look set to "die out".
I think you're seriously misinformed. Neither the Y chromosome nor males are dieing out. Even if we were to go, so would women. So it's not like they'd "win".
It is true that the Y chromosome is slowly getting smaller (over tens of thousands of years) but to extrapolate to zero would be like looking at the reduction in size in computing power over the last several decades and concluding computers will one day vanish. | |
|
| Evolutionary question?
Posted: 1/29/2008 9:46:28 PM | Just small clarifications....
Im not sure its proven were from apes, they were thinking of fish also? etc.
Proven beyond a doubt? No. Proven beyond a reasonable doubt? Yes. The genetic and fossil evidence is very conclusive. And we could actually have come from both apes AND fish, assuming apes came from fish if you go back far enough.
If I know something about biology its that EVERYTHING has a reason and makes sense.
Gotta disagree there, too. Evolution works by the introduction of mostly random mutations, so while natural evolution goes on there will always be random "junk" in the genetic pool. Most of it is never noticed because it's not expressed physically, or not dramatically so. And remember, at any given time, including now, there will be genetic dead ends in existence. | |
|
| Evolutionary question?
Posted: 1/29/2008 11:44:59 PM | Well... The process of the diminishing Y chromosome is one that will take thousands of years (or so I've read), but you do have to wonder, it's functionality is on the decrease to the point that the male sex itself could be under threat.
Unless of course (and remember, this is all highly speculative anyway), males will simply have one X chromosome (along with some genetic "junk") while females stick with two.
Anyway, our knowledge on genetics now is very limited and extrapolations into the future are imprecise at best. But it does make you wonder just how the sexes will evolve over time. | |
|
NOX813
|
Joined: 11/20/2006
Msg: 43 | |
| Evolutionary question?
Posted: 1/30/2008 11:28:29 AM | HA HA! The question in it self is paradoxical. If one celled organisms needed no sex to procreate-why do we have sexes at all other than the fun.   | |
|
| Evolutionary question?
Posted: 1/30/2008 12:07:01 PM | | It's also possible that the determination of sex could migrate to another chromosome. But if males die out and science doesn't find a way to solve the problem (through cloning, etc.) then females will die out with us. Frozen sperm will only go so far. I really don't think this is anything to worry about. We and everyone we ever know will be long gone before this happens (barring radical medical/scientific advances). I think it's more likely we'll direct our own evolution before then. | |
|
| Evolutionary question?
Posted: 1/30/2008 6:12:21 PM | So many misconceptions.
Loss of the X-chromosome will not necessarily cause a loss of males. Many animals have a W/Z chromosome system, in which females are the ones with an effective "X" chromosome. Many animals have their gender determined by temperature or by hormones. In some cases, this is combined with differing chromosomes - sex is determined by the chromosomes...unless certain conditions alter the results. Ultimately, the X chromosome simply carries a code which sets in motion a chemically induced sequence of events which causes a female pattern to become male. There are other ways of inducing that chain of events, and loss of the X would likely be associated with an alternate control method already being in place, such as cross-over error which moved the genes to another chromosome.
How about loss of sex? Unlikely. Contrary to the suggestion regarding killifish, a trend to parthenogenesis isn't the case. Sex arose with bacteria. It's been around for more than 3 billion years. Without it, genetic variation [and evolution] is limited to the random changes in the individual. That's not much. Sex allows the genetic variation in one individual to be shared with the variation in every other compatible individual. That multiplies the variation tremendously and allows an entire population to adapt. Basically, without sex, every species is a mother and all her nearly-identical descendants. These lack the genetic variety to adapt to a change in selective pressures. Apply a new selective pressure - every member of the species is likely to die. Over the long term, this will gradually eliminate the majority of parthenogens. What's the result? Only the sexual have the ability to adapt. Evolution favors sex.
And loss of males? This would not necessarily eliminate females or the species. First, if this is a genetic change [as implied by comments about reduction of the X chromosome], then who the hell is passing on the genes that make males? Those without maleness cannot pass on maleness; so whoever IS reproducing is, in most cases, passing on the tendency to gender. In effect, a sexual species cannot just gradually become unsexual.
So how ABOUT parthenogenesis? Most cases of parthenogenetic species I know of are the result of genetic flaws which come about by hybridization of closely related species. The effects are instant. All hybrid offspring are female, and they all produce clones of themselves without fertilization. In some cases, a random error will cause the production of male offspring. This may result in a reversion to sexuality in at least part of the population, or it may lead nowhere, or it might lead to a new sexual species. What are the benefits of parthenogenesis? Not many actually. It allows that one "lucky" female to rapidly exploit an environment without worrying about finding a mate. If the parthenogenesis is facultative [ie, a species CAN reproduce without males, but normally doesn't], than a stranded female can produce male AND female offspring, resulting in a population which starts as clones, but rapidly gains the benefits of genetic variation and sexuality.
Of course, if a selective pressure comes to bear before there's been time to adapt, the result will be the same as for any other completely non-sexual species: rapid extinction.
Long and short of it:
Loss of males is not likely. If males are lost, it would likely lead to extinction of the species, but it's quite possible males could re-appear later anyway. There is no trend to loss of sexuality overall - just the opposite. Loss of males is a short-term and rapid solution to low population issues, but it's a temporary or dead-end solution. | |
|
| Evolutionary question?
Posted: 1/30/2008 6:43:19 PM | Interesting thoughts Frog.
What about our diminishing sperm count? Is that purely environmental or are there genetic factors too?
After this article on the evolutions of males I read a while back, I got the distinct feeling Mother Nature had it in for us. Diminishing Y chromosome AND sperm cells LOL. | |
|
| Evolutionary question?
Posted: 2/4/2008 7:47:21 PM |
he simple fact that humans are taller today has to do with healthier children which is a function of the choices the female made.
sorry, but it seems that humans are taller today in societies where they eat more and better. Nothing to do with female choice | |
|
| Evolutionary question?
Posted: 2/4/2008 10:09:00 PM |
Contrary to the suggestion regarding killifish, a trend to parthenogenesis isn't the case
Aww, you're no fun. Why let facts get in the way of a good story?
They're weird little fish. Bruce Turner, for one, has made a career out of them. He's the guy that at 17 wrote the "Enjoy your Killifish" book all petshops had in the 60s.
http://www.flmnh.ufl.edu/fish/Gallery/Descript/MangroveRivulus/MangroveRivulus.html
"Functioning as hermaphrodites, the mangrove rivulus is able to fertilize their own eggs internally, producing viable offspring. Each hermaphroditic fish produces both sperm and eggs in it ovotestes. It is the only natural example of cloning by a vertebrate organism. Males are rarely observed in the wild in Florida, but are more common throughout the Caribbean and Central America. There are two types of males, primary and secondary. Primary males develop directly from fertilized eggs while secondary males develop from hermaphroditic fish under certain environmental conditions. There is evidence that young fish sexually outcross, releasing unfertilized eggs, with the occurrence of both males and females in wild populationsl There may be an age-dependent shift in sex allocation, from female-dominated to one that is hermaphroditic-dominated as older populations have significantly higher numbers of hermaphroditic fishes. This hermaphroditic mode of reproduction may be an evolutionary response to the habitation and possible isolation within crab burrows."
And we could actually have come from both apes AND fish, assuming apes came from fish if you go back far enough.
Have a look at this:
http://en.wikipedia.org/wiki/Recapitulation_theory
My kid is doing this in grade 11 science. They still teach strong recapitulation. Here we go again with dragging the school board kicking and screaming into the 21st century. | |
|
| Evolutionary question?
Posted: 2/5/2008 6:59:26 PM |
It is the only natural example of cloning by a vertebrate organism.
Apart from kleptogenesis in Ambystoma hybrids [which occur naturally, though they do not breed true], whose offspring are mixes of hybrids, clones of parental ancestors, and sexually produced ancestral species.
Apart from clonal parthenogenetic species of Darevskia, Kentropyx, Aspidoscelis, Rhamphotyphlops, and spontaneous parthenogenesis of clonal Varanus...
The distinction of the fish you mention is its hermaphroditism...but I have hunch I've seen evidence of it in other species, also teleosts.
BTW - the latest issue of American Scientist has a great article on pupfish evolution, development, and plasticity. | |
|
| Evolutionary question?
Posted: 2/5/2008 11:06:16 PM | Interesting article. I knew a guy, a bit of a pariah, that illegally removed some in the mid 80s and reared them. He found the same thing - they're different outside devils hole. Pupfish really are cool little critters, they act more like cichlids than killies in so many ways.
Lots of fish change sex, but I'm not aware of any other hermies.
One interesting thing that came to light in the past decade was the skewed sex ratios of killies. In live bearing tooth carps Norton pretty well established what environmental factors determine sexual dimorphism, but the riddle has never been solved for egg laying ones. And still isn't. OF COURSE this happens for rare, expensive and stunningly beautiful ones the most, for example Rivulus xiphidius. Two guys living on the same street under what appear to be the same conditions will get 98:1 sex ratios, bit one males, the other females. While we still don't know why, one guy has demonstrated that if you raise them two to a tank then they overwhelmingly develop as male and female.
Here's hoping the sping C. diabolis count finds more than 38 fish this year. Here's hoping they find fish at all. | |
|
|
|
Home
login 
