I HAVE READ THAT this is a kind of law of nature like To EvOLVe..if breeding takes place in the same family slowly the genes will deteriorate..IS THAT SO???
205927
Inbreeding is breeding between close relatives.\n\nIf practiced repeatedly, it typically leads to a reduction in genetic diversity. Inbreeding often leads to reduced health and fitness (called consanguinity depression, inbreeding depression); however, livestock breeders often practice inbreeding, then cull unfit offspring, especially when they are trying to establish a new and desirable trait in their stock.\n\nAn inbred individual is likely to possess several physical and health defects, in addition to higher incidence of inheriting a poor trait. They include:\n\nreduced fertility both in litter size and in sperm viability \nincreased congenital disorders \nfluctuating facial asymmetry \nlower birth rate \nhigher infant mortality \nslower growth rate \nsmaller adult size \nloss of immune system function.
44713
Ahem. People, he's asking about the RATE of change. Not whether changes occur or whether evolution occurs. He clearly already knows that.\n\n__________________________________\n\nWell done. You’ve asked one of the most controversial questions in current evolutionary biology.  Much debate rages about this subject right now. \n\nWhat you are describing is commonly referred to as the evolution of evolvability. As you point out, if a population doesn’t have sufficient variation then environmental change could lead to extinction. But at the same time if the population is too variable the outliers will simply perish in current conditions. For example if elephants contained the inherent variability to produce young twice as big or the size of a rabbit those individuals would die.\n\nThe belief was for 100 years or so that the selective pressure of current environment would maintain a fairly tight rein on variability, that mutation rates were approximately constant and that survival in times of change was simply a case of pot luck. But then people started to look at the fossil record and the real world and it seemed like that wasn’t plausible. Novelties seemed to appear almost overnight, and they appeared almost any time they were needed. \n\nSo then came the concept of punctuated equilibrium. The idea that  a population would sit still for long periods, then as conditions changed they would suddenly leap forwards into a radically different form. That was all well and good, but it was basically just a restatement of the observations, not really an explanatory theory.\n\nIn the past 15 years ago there has been a lot of debate about the idea that organisms have evolved to evolve. That they have evolved in such a way that they are physically stable in times of environmental stasis, but when the environment becomes stressful change they can either mutate more, or reshuffle genes or express pattern of dormant genes to produce stable phenotypic novelties at rates that far exceed background rates.\n\n\nThe theory certainly makes sense. It’s hard to argue that such a trait wouldn’t; be a survival advantage. Unfortunately the evidence is ambiguous. And at the moment there are umpteen dozen theoretical mechanisms to explain how it could occur, and they are impossible to separate out. There is some work which has shown that many species can open up dormant genetic material for expression and re-assortment in response to stress (see first link below). And some experimental evidence suggests mutation rates increase in response to environmental change. Some say that prions are the key. Other favour inherent genetic instability in those individuals that survive initial changes, meaning that the decedent population is inherently prone to genetic varaiation until the environment stabilises and kills of the outliers again. Other propose that assortment of populations within the same or closely related species could explain it. But at this point we can’t even prove that genetic variation does change under stress. But at this point we just don’t know. \n\nYou ask a damn good question but the concept is hard to study and harder to establish with any certainty.\n\n_______\n>>>>Being able to actually understand how, and under what\n>>>> circumstances mutations happen strikes me as extremely\n>>>> important.\n\nWe've actually got a pretty good handle on how and when mutations occur. This is more of a question of when they are expressed or encouraged. Organisms have the ability repair genetic damage thorugh several mechanisms. They also have the ability shield the nucleus fom many mutagens. The issue is whether they may be able to damp down those processes to encourage more mutations.\n\n>>>> I can definitely see that species that do not have the \n>>>>capability to mutate in response to external forces\n>>>> would be selected against.\n\nYes, it's a rather hard
468705
Not all changes in a species reflect changes in the genome.  In the case of height, it reflects improved nutrition, and improved general health due to sanitation and reduction in childhood illness due to vaccination.  Since we are probably approaching the limits of the environmental factors, evolutionary forces will seek a new equilibrium.  The evolutionary forces that create advantages in height in a post-industrial society will be different than in our agrarian past.  We have crafted our environment.  Will there be a survival advantage for not having to duck through doorways?  Many factors will be social.  Height can be used to intimidate, which may help in getting a raise.  There's the old cliche, "tall, dark, and handsome".  How much will height help in getting a "better" mate?  Lastly, with environmental factors balanced accross the species, will we see a tendency towards uniformity at an optimum height.  It may turn out that the variance will be more telling than the mean.  The next 10,000 years will give us a hint.
101609
yes but we screw it all up - evelutionary caches (ie the aboriginies of austrailia) if left alone would eventually differ enough to become a separte species - for better or worse. but with world travel this is very unlikely to happen.\n\neven moreso with modern medicine we are hampering the natural selection process and genetic inferiority and deformity are not lost (i know this sounds heartless but nature has its own plan) we keep the week and infirm alive and in many cases protected form certain natural demise.\n\ndo I believe evelution is at work... yes but in humans its sort of devolution :S\n(sorry went on a rant :P)
314409
Since life came about through the process of evolution, that means that genetic mutations allowed some species to survive while others did not. That being said, a genetic mutation would render an offspring different from it's parent. For instance, if two birds mated and a genetic mutation occured, the offspring would have traits that make it different from it's parent, therefore it would not necessarily be the same though it came from two of the same species. Changes in speciation had to happen at some particular sharp point where a species would diverge from its heritage. Therefore if an egg was laid by a bird that was not a chicken, but the embryo inside the egg had the mutation that makes it a chicken that would mean that the egg came first.
51494
"Breeding" looks like it fits the bill.  \n:-)  Hope this helps!
145367
Gene pools do work together in co-operation against competition w. other gene pools while competing internally, so w. in families yes.  Mating wise we seek out characteristics that will compliment our own genes, often opposites.
470166
Put in simplest terms, naturally occuring genetic variation gives some species, and some members of species a competitive advantage over others. Call these variations ADAPTATIONS, and environmental factors NATURALLY SELECT for organisms that have these adaptations, and select AGAINST organisms that do not have these adaptations. Thus, those that survive (the fittest) pass these adaptations on to their offspring, and those that do not have the adaptations, die off. Keep in mind this selection takes many many many years. \n\nThe nature of sexual reproduction is to create variation, and variation will be in either "direction of a phenotype" (a person who is 6'0 will have children who are 5'10, 6'0, and 6'2 for example). This is the nature of inheritance.\n\nNow, lets hypothetically say that we were all at one time "species X". The average member of species X can run 6mph. Well, some members can run 9mph, and some can only run 3mph, again by nature of inheritance. Well, if food were running short lets say, or any situation that "selected" for faster species members, everyone who ran LESS THAN 7mph would die, and those who ran GREATER than 7 MPH would survive.\n\nSo now when this population of faster runners reproduces (7mph,8 mph, 9 mph), their offspring will run, again by nature of inheritance, maybe between 6mph - 12mph (as opposed to 3mph - 7mph). Lets call this group now SPECIES Y. \n\nSuddenly, perhaps more food is available, and speed is no longer a selective advantage. Well, variation will continue to occur, but this time, slower members will not be selected against. So, some will continue to be slower, and some will get faster. The ones who get faster, are Species Z. The ones who didnt get faster, remain Species Y. But both have survived because nothing has selected against them!!!\n\nSo looking at humans and their "evolutionary predecessors", remember that humans have slowly been removing themselves from any competition with apes. Only this time don't look at speed, look at many many traits (intellience, walking on 2 legs, opposable thumbs, etc.) We have been able to find our own food, and are involved in littlle competition with them for quite some time now. \n\nWhen thinking about evolution, you must think BIG PICTURE. That's how I always saw it. You must think who is gaining SELECTIVE ADVANTAGES because of ADAPTATIONS FOR SURVIVAL, and who is going to be at SELECTIVE DISADVANTAGE based on COMPETITION AND LACK OF SURVIVAL.
51761
it's an application of the Hardy Weinberg Law.  page 8 should help you out.\n\n\nhttp://www.zoology.ubc.ca/genetics/334-1998/pop.pdf
660424
Whoa, you tackled a risky one there and will probably get some interesting answers. \n\nI will say that I am concerned in that modern science has made it possible for many to live in spite of genetic traits that can continue to be passed down to other generations. In days gone by, the less healthy did not usually make it to the age in life to procreate and so there was a natural termination to many of the genetic problems. \nNow  in the modern world, our morals and values have to enter in and whether we could with good conscience do what nature once did is debatable.\nFYI...I would have been one of those that was buried beside the Oregon trail with the epitaph...because of her delicate constitution,she did not make it.\nAntibiotics have saved my life at least 4 times to date.
267086
No. Variation only indicates limited change.  Yes, there is indeed variation, but as far as such drastic changes as Evolution indicates, the changes that must occur for Evolution to be true do not occur.  The change is not that drastic.\n\nThere are limits to the changes.  Our own tampering with fruits and vegetables show that we may "create" a new fruit or vegetable, but seeds will not be produced.  It is because we have caused an unnatural thing to be produced.  \n\nYes, there are definite "Laws".
120860
Biologically it's wrong, since if your father were to have sex with your sister and they were to produce a child, that child could have all the heritable traits from that family times two, and in that case it weakens the species, as you can see in royal, insestuous families who eventually died out because of heritable traits that became heightened because of the lack of genetic diversity. Imagine those people procreating with others outside of their family after such an incestuous line, it could weaken an entire gene pool! \n\nPeople are born with a general sexual aversion to their parents (although Freud would argue with me) and as we grow older and spend all our shildhood days knowing and respecting our parents, siblings, and grandparents (etc.) we absolutely block inscetuous thoughts from our minds. It's become a taboo within many cultures, but I think from the legal standpoint, it is illegal perhaps mostly because of the biological reason I mentioned above.
349639
Well if they ensure that the mate a homozygous dominant with a homozygous recessive (eg B/B x b/b, as is the case in monohybrid crosses, you can make sure the parents have this genetics by watching them over generations, mating only dominant with dominant and recessive with recessive) then you'd know that for a diploid plant/animal, as all offspring get one gene from one parent and one from the other, all of the F1 would have to be B/b - so heterozygous for that trait. So they'd all be the same genetically for that particular trait! But then if you crossed the F1 with one-another they wouldn't all be the same... crossing heterozygotes youd get some B/B, some B/b and some b/b...
100132
As a biologist I must weigh in.\n\nThe terminology and methodology of you stance is a bit off.   As we populate and compete for resources that are scarce, there will be increased competition. Problem is that the way the world works, that has little bearing on the real world. In Africa kids starve daily. In America kids are obese. There is no natural selection taking place.  As the population expands, there will be groups of HAVEs and groups of HAVE NOTS. But the HAVES will have few external influences on their mating.\n\nHomesexuality has been around a long time. It is seen in animals, and people. Throughout history at times it was commonplace and accpeted. Regardless of what you may read, no one can say for sure the causes of homsexuality. It is probably a complex set of genetic variations, behaviors and experiences. It could be genetic, as some familes have high incidences of homosexual members, but it is probably more spontaneous.  \n\nAs an aside, it is patently FALSE that states which have gay unions have a falling birth rate. You quote the need for references, put your money where yuor mouth is. Lets look at those few states and look at the birth rates and all the variables and see the true facts.\n\nback to the question. No, as a species we are not evolving towards gay. If population is a true evoluntionary problem, people will become less fertile, as many animal models ahve shown. Numerous species where competition is tough have fewer young and would be less likly to produce offspring regularly. That is how mother nature operates.\n\nif anything, the evolutionof our species will ultimately end in parthogensis where women can self fertilize making males obsolete. If we were to model the human species against animals we would see similarities in population dynamics and this could be the future in MANY thousands of centuries.
67873
If you have offspring from a first cousin, chances are good they will be a burden to society due to their mental and/or physical limitations.  Inbreeding breeds mutants...
420356
Of course. It lead to genetic isolation, then evolution which gave us new species. Look at the ratities as an example.
232701
It could be argued that some family trees in the deep dark south don't have branches, but are straight lines. Inbreeding happens, no matter what color you are.