| Evolutionary question?
Posted: 2/9/2008 4:03:44 AM | | Interesting.****oaches and some species of Scorpion also reproduce asexually when there is a lack of males around. It does seem as though most of these asexual babies are clones of the mother, so the need for genetic diversity would require sexual reproduction to be the preferred method. But it would be a useful trait, regardless. Imagine if women had sperm for when they didn't have males around. | |
|
| Evolutionary question?
Posted: 2/9/2008 4:31:39 PM | Actually, if they had sperm, it would be sexual reproduction. That requires either males or hermaphrodites to be present in the population. When we speak of parthenogenesis, no sperm is involved, only the egg. This is possible usually because the egg has failed to divide properly, and is diploid rather than haploid. This may be induced directly by temperature, by genetic incompatibility due to hybridization, or due to hormonal cues resulting from temperature, population density or balance, hybridization, mutation, etc. Similar cues can induce males to develop from "female" eggs. Interesting, some species of Aspidoscelis require pseudomales. These are just clonal females which behave like males, with the simulated mating behavior being a trigger for development of fertile eggs.
Insofar as sperm storage is concerned - many species do, but they have to be fertilized by males first. Many female snakes can retain viable sperm for years. | |
|
| Evolutionary question?
Posted: 2/9/2008 5:21:46 PM | | My mistake. I was getting****oaches confused with tapeworms, which have both male and female reproductive organs. | |
|
| Evolutionary question?
Posted: 7/5/2008 8:52:34 PM | | Biological evolution is no longer occuring in humans. According to the Hardy-Weinberg equillibrium, if natural selection is not occuring within a population there can be no evolution. Humans that would've otherwise died out without technological advancements are living to reproductive age today and many of them do reproduce. | |
|
| Evolutionary question?
Posted: 7/5/2008 9:21:53 PM | To answer the OP's original question:
Women made their contributions early on, by staying with the fire to keep it going. Men were sent out to kill tigers because they couldn't be trusted not to p1ss on the fire... | |
|
| Evolutionary question?
Posted: 7/6/2008 4:52:51 PM |
Biological evolution is no longer occuring in humans
Patently false. We are no longer preyed upon by sabretooths. We are no longer trampled while hunting mammoths. Mates are still selected by their behavior. Mates are still selected by their wealth, health, or "beauty" [which is, essentially, a measure of how 'average' a person is]. Survival is also determined by behavior: humans enlist in high risk jobs as soldiers, police, firefighters or gang members. They may profit, they may die. They may undertake risky passtimes like skydiving, car racing, or just speeding while driving drunk. They engage in bar brawls with knives and guns. Humans cheat. The wife or girlfriend gets pregnant by another man. The husband or boyfriend has five women pregnant at the same time. For THIS man, any genetic tendency to cheat is positive, because that gene isn't just passed on - it's passed on over and over.
Natural selection cannot be avoided or eliminated. The pressures simply change in nature. Even in a space station's artificial environment, natural selection will be at work. This may entail a loss of dependency on symbiotic organisms, increased vulnerability to disease, loss of body mass due to lower gravity, sensitivity to types of lighting or atmospheric mixes. If these pressures are not deliberately imposed in order to cause genetic change, they are "natural". They occur at random due to environmental pressures imposed on random genomic variation. Resistance is futile. | |
|
| Evolutionary question?
Posted: 7/6/2008 10:49:22 PM | The link below leads to a story countering the belief that human evolution has stopped. It makes a very potent argument that the inverse is actually true due to the crowding of individuals on the planet and the ease of travel. Moreover new stressors now exist that spred faster and further than before forcing selection.
http://www.news.wisc.edu/14548
However, I have read compelling arguments that the human brain will not evolve much further that its present form. I have my doubts that this is true. Intelligence is increasing steadily in developed countries. Whereas this may not have a physical cause, I see it as evidence that physical changes may be taking place and cannot be easily ruled out. | |
|
Home
login 
