Mokele

How can genes for longer teeth in a lion spread *without* growing a full lion and witnessing the selective effect on the organism? Genes don't die or find mates, organisms do, as *collections* of genes. If selection occured at the genetic level, each gene would be acted on separately. The occurence of linkage groups alone disproves this, not to mention developmental genes. Let's try sickle-cell. Is that allele good or bad? The answer is, you don't and *can't* know. Not until you have an organism and an environment (with or without malaria) for it to interact with. Lions don't just kill the genes for poor running in the unfortunate mutant gazelle they catch, they kill and eat the whole animal, all it's genes, good and bad. There *are* instances of gene-level selection (transposons would be one), but for the vast majority of the time, it's the organism which is acted upon by selection. (Aside: Oh, thank f-ing god, a real evolution discussion, noT just squabbling with creationists!) Mokele

Damn, I didn't even notice that! Duh! (And gametogenesis is the process by which your body cells make gametes, namely sperm and eggs) ...and this is why I usually preface anything I say about molecular studies with "it's not my field, but..." Mokele

I figured this was more appropriate than the Computer science forum, since this is more of an electronics question. I've noticed that many computer power supplies have a label on them, listing things like "+12V, 15A" and "-12V, 0.3A" and suchlike. I know the V and A mean volts and amps, but I'm a bit unclear of the meaning of the + and - signs with respect to voltages. Isn't voltage always a difference in potential, thus doesn't get a sign like that? Basically, I want to hook something up to the power supply with a 2 Ohm resistance, and I want to know what wires to connect it to. Mokele, probably well out of his depth on this project.

Bwahahaha! I shall do worse, and use my powers for 3\/i1. Pheer my leet power!

Well, it doesn't cause them so much as make them more likely. Imagine if a person has one copy of a defective allele of a gene (basically a bad copy) which is so rare that only 2% of the population carries it (has one copy) and a hundredth of a percent 0.0001 express the disease form (two copies). Now, imagine this person, A, had a kid, B. This kid, because of inheritance, has a 50% chance of having the defective allele. So now we have two scenarios: In scenario 1, Kid B grows up and finds some random person, X, to marry. Statistically, B has a 50% chance of having the gene, while X has a 2% chance, give or take. When you work through the numbers, that means that there is only a 2.5% chance they'll have a kid who expresses the disease form. In scenario 2, Kid B mates with mommy A. Because mommy A *definitely* has one copy, and kid B has a 50% chance of having one, the chances of the kid having the disease is 12.5%, 5x higher. This repeats at *all* loci every time there is a mating, and given that most humans have some recessive disease alleles, this simply means that inbred kids are statistically more likely to express deleterious mutations. Mokele

No, more like Game to Terminology Screw-ups... The results still mean that those were not the only humans alive at the time (otherwise we'd all be so inbred that 'Dueling Banjos' would be the most popular tune on earth), just that the 'most recent common ancestor' is going to be different for every chromosome and possibly every gene. Mokele

Duh, my mistake. So that final formula possible formula would be F = T/2L + T/L, i suppose. That'll teach me to go from memory rather than my notes, while posting on an empty stomach... Mokele

Hrm, you know, you're right (at least about me not being correct). Because I focus so much on a macroevolutionary time scale, most recent common ancestor usually refers to a species in my experience, and I forgot that, because of independent assortment of alleles during gametogenesis, there would quite possibly be a different 'common ancestor' for each chromosome (and possibly each gene, depending on recombination frequency). Perhaps a better term for them is in order... Whoopsie... Mokele

Ok, this is just ridiculous, and has degenerated to the point that no further productive discussion will occur. Closed.

Ok, I have a question about a simple, but not so simple, system. Let's say I have two rigid, massless poles of length L, joined by a massless, infinitesimally small motor that exerts torque T. If the poles are parallel, and I stick one into a concrete wall for anchoring, obviously the motor will move the free pole. Plus, if I push down on the tip of the free pole, I should need TxL newtons of force to prevent movement. That's simple enough, good old levers and such. But what if I attach another motor to the tip of the free pole, and another pole to that motor, so I have 3 poles in a line, joined by two motors? (another way of imagining it is like your arm, bending at the wrist and elbow) Do I have Tx2L + TxL acting on my hand at the tip of the furthest pole? Put another way, if there's a lever at the end of the lever, do you add the effects? Or, hopefully better, Here is a very crappy drawing (since I suck at art) of the system, and I'm basically trying to find F in terms of T and L that keeps the system static Is F = Tx2L + TxL correct? Am I phrasing this horribly? Mokele

Another, less benevolent source of such chemicals: Many plants produce and exude chemicals from their roots to kill or weaken any other plant (or other plants of certain species) that tries to grow near them. Plants are just a vicious as animals, but they have to use chemicals rather than teeth and claws. Mokele

They're pretty cheap from various online sources. I've got one of my own, about 3 inches long, that I paid about $12 for, iirc.

But the process of inbreeding itself is *not* selective. Inbreeding causes alleles to increase in frequency without regard to their positive or negative effects, but instead purely by chance. That's why inbred populations have so many more birth defects. And it's been experimentally demostrated that fitness is significantly lowered in inbred populations compared to non-inbred populations. That's my point. It will affect gene frequency, yes, but in a random way, and *certainly* not in a selective way. Natural selection is only slow in large populations with reduced genetic variation. The reason we got dog breeds so fast is because a) we've had tens of thousands of years to get them, b) canines are pretty geneticly variable anyway, especially when protected from normal selective pressures by living in captivity and most of all c) by "line-breeding" and breeding for specific traits, we are, in effect, imposing very strong selective pressure on a small population, resulting in rapid change. In inbreeding of domestic dog breeds is not a mechanism of their overall change, but a side effect due to humans using unusually small and closely related populations to cause even more rapid change than usual. If we breed a dog for height, it's natural (or rather, artificial) selection that makes the population get taller over the years. If the population is inbred, that has nothing to do with the process of them getting taller, only the reason why they display numerous unrelated genetic defects, such as bad eyes, deafness, heart trouble, or gastro-intestinal ailments. Intense selection on a small population is why dog breeds changed so fast, not inbreeding. Inbreeding just explains why they're so damn unhealthy and generally just screwed up. Just because it causes change faster doesn't mean it's what actually happens. Remember, the fast changes we see in punctuated equilibrium still take thousands and thousands of generations. Inbreeding is not selective, and therefore cannot produce adaptation. Only natural selection can produce adaptation. Also, "unnatural selection" is not the correct term for it. Mokele

Oh, I agree that it doesn't have to be beneficial, and I agree that it does have a place in what happens during bottlenecks or founding of population. Mostly what I was disagreeing with was that it seems you were arguing that in some cases it could be beneficial, which I don't agree with. Statistically significant, yes, but not beneficial. I'm unclear what you mean by this. Do you mean that new individuals would join the original, inbreed founder population? But inbreeding isn't *necessary* for these rapid changes, only a small population size, which can still mean several thousand individuals. While inbreeding can cause fast changes, it also makes them in a totally non-selective way that results in decreased fitness, since more the changes are negative than positive. Basically, I see it a potential factor, but I'd also argue that any population for which it became a *major* factor would be *really* screwed in the long term. The fixation of so many negative traits and the loss of diversity would mean that the population would probably be outcompeted by the first non-inbred population to come along. After all, inbreeding has produced major and rapid changes in domestic dogs, but it's also produced animals whose eyeballs simply fall out or who can't stop drooling or whose hearts are so overstrained they typically die before middle-age. Mokele

Of course. I was simplifying for ease of explanation. Only males have the Y chromosome, which they can only inherit from their fathers. Similary, for the mitochondrial eve, while both males and females have mitochondria, only the female contributes them to the offspring. How would this not make adam the most recent common ancestor? By definition, the term means he's the most recent human ancestor which all living human males are descended from. Ditto for the mitochondrial eve. As for the usage of "most recent common ancestor", I'm not really sure how the term can be unclear. It's the most recent person who's on the family tree of *everyone*. Like the most recent common ancestor of me and my cousin is my grandparents. Mokele

Couldn't one also argue that having a pledge recited day after day by thousands of kids who don't know (or care) what it really means, and are doing so purely because that's just what you do in school, cheapens the pledge and erodes the true meaning and feeling behind it until it's just another mindless recitation? Mokele

Um, I unfortunately have to contradict you on that. We did get several signatures in chemistry class, iirc. But then again, southern public schools aren't what you'd call the apex of education... Mokele

I think so. Let me try again. You have a family tree, as do I. If we trace it back far enough, we share a common ancestor. But Bill isn't in that group, we have to trace our lineage further back still until we find the common ancestor of you, me and Bill. Now imagine you, me and bill are the last people on earth, and Bill dies. Now the most recent common ancestor of humanity is *our* shared relative, since Bill no longer matters. That doesn't mean that Bill never existed, or that his family didn't exist alongside ours, but only that our common ancestor is the common ancestor of all *living* humans. So, the Y-chromosomal Adam is the last common ancestor of all living males. Other males lived alongside him, but their lines eventually died out (like bill), otherwise we'd have to push back the common ancestor further (like we did when finding the ancestor of you, me, and Bill). Does that help? Protiens can be affected, depending on their charge, but, so far as we know, DNA is not. There seems to be little or no mutagenic power of EM, though, at least not until it reaches an insanely high level (beyond 'head in the microwave' level). I recommend both this site and http://www.talkorigins.org In the latter, you can find all the evidence you want, and in the former, you can ask questions about anything you might be unclear on. Just remember to weigh all the evidence before committing. Great, but not infinite. There are constraints on evolution and adaptation. An excellent example is the evolution of fast-moving herbivores in the Cenozonic (aka 'Age of Mammals'). Both Perisodactyls (odd-toes, like horses and rhinos) and Artiodactyls (even toed, like deer) evolved in North America, Europe, Asian, and Africa to fill the niche of a herbivore who can run fast to escape predators. In South America, which was isolated, a nearly identical, but unrelated lineage, the litopterans, evolved (and only went extinct when their isolation ended). But Australia never evolved a fast-running quadrupedal herbivore, especially with hooves, like everywhere else. Instead they got the kangaroo, which is fast, but less efficient. Why? Becuase kangaroos are marsupials, and evolved from marsupials. And marsupial babies must crawl, with their arms, through their mother's fur into her pounch. A baby with legs modified for fast running would not be able to make such a climb, and would die. So in this way, developmental biology and past evolutionary history constrained and limited the possible adaptations of a group of organisms. in layman's terms, they got stuck in a catch-22. For more on this *very* interesting sub-field of biology, look at some of Gould's essays. Mokele

Well, close... The mechanism by which a small segment of the population becomes isolated *is* an important mechanism of evolution, called genetic bottleneck or founder effect depending upon whether it's caused by disaster or colonization of new habitat, repsectively. And inbreeding probably *does* contribute to the fixation of alleles in populations in the circumstances you describe. The problem is that inbreeding actually *decreases* what evolution has to play with, and would therefore be detrimental to the long-term survival of the population. It increases the chances of homozygosity at any one loci, meaning that evolution must wait for new mutations rather than acting on existing variation. It also causes homozygosity and fixation of alleles *without* regard to selective pressures, which is why you see so many lethal and barely sub-lethal birth defects in an inbred population. Another consequence of the loss of heterozygosity that comes with inbreeding is the loss of diversity of alleles in the Major Histocompatability Complex, which plays a large role in the immune system. I'm not totally up to date on immunology, but I do recall it being established that the immune system requires as much diversity in these genes as possible, and loss of that diversity results in a weaker immune system. In short, I don't think it's defensible to consider inbreeding adaptive or beneficial, even in the circumstances you describe. It *does* have an effect, especially in the situations described, but I'm not convinced it would be a positive one (or reliably enough so to be considered adaptive or beneficial). Mokele

I can annecdotally confirm this, to a degree. Several friends and I worked on a similar petition during high school for a few weeks. We got about 50 or so signatures, including teachers and honor students before even *one* person caught on. Penn and Teller did something similar in their show "Bullshit" (which I highly recommend, btw), with similar results. So yes, people *really* are that ignorant. Mokele

The nature abstract says: "at intermediate speeds it finds a new pendular-running gait that includes walking and running as extreme cases." I can't get at the article itself right now, but I tend to be suspicious of purely-model-based methods that do not empirically confirm their findings. Such tests would not be hard, either. You just need a respirometer and some volunteers. Hopefully I can find the full-text later. Mokele

Ok, a bit of clarification about the Mitochondrian Eve and Y-chromosomal Adam: Basically, all living humans are descendants of these two, who a) Did *not* live at the same time and b) were *not* the only humans alive at their respective times. Imagine we have a troop of primates. One male has an *exceptionally* good gene, which allows more survival and reproductive success for his offspring compared to others. The population is stable. Over time, the mutant male will compose more and more of the population, until the last remnants of the non-mutant lineage die out. At that point (and from then onwards) that original mutant male will be the common ancestor of all those primates. But there *were* other primates around; they just lost the evolution game. Another analogy: All birds are desendants of Archaeopteryx (for the sake of arguement). But that doesn't mean Archaeopteryx was the only theropod dinosaur, or even proto-bird, alive at the time. It just means that all the *other* family lines are dead. This doesn't mean diddly-squat about faith, or interpreting Genesis more broadly or narrowly. Personally, I think Adam and Eve is a story based on the knowledge of the time, which didn't include things like the effects on inbreeding. If we went back in time, showed them a Chihuahua and said "inbreeding will do *this* to wolves", they'd've burned that section of Genesis faster than you can say "Horrifying rat-like, bug-eyed abomination". Heh, we should use that as an arguement for selection causing major morphological change. We turned a dog into a rat. A bug-eyed, bald, Parkinsonian rat. Mokele

I think there's also an example of "common-man" populism in such things. People don't like the idea that they're too dumb to grasp the workings of the world around them, and don't like that this information must be dictated by experts, and so they rebel, jetisoning these complex theories for simple, if wrong, explanations. Notice how most creationist objections are "common sense vs evolution", with the undertone that the creationist, a 'common man', can take on these experts and show himself to be better. Mokele

The predominant sexual attraction to members of the same sex. We know there's a genetic component, but there is also an environmental component. The search for both is ongoing, but the latter is most likely in-utero, and at most before age 4. No. While the so-called "ex-gay" organizations claim so, actual investigation reveals a success rate on the long term of 0%. They can put people into denial, but not actually change anything. Incidentally, the leader and creator of the largest of these organizations left them and ran off to canada with his same-sex VP to get married. Bullshit. Humans are not "meant" to be or do anything except possibly to be a group of troop primates without body hair and with lots of tools. Homosexuality is common in nature, in everything from whales to beetles. As for "OK", what makes you think it isn't? Nobody's being hurt, it's two consenting adults, so what gives you the right to proclaim it "not OK"? No, that's factually incorrect. Abuse does not lead to homosexuality. Funny you should say that, because there's a warning for intolerant/racist remarks on this forum, which you should be receiving shortly. Receive it a few more times, and a nice little ban will shut you up. If you want a reasoned discussion, that's fine, but do so without the disparaging and intolerant remarks. Mokele

Ok, time to end this stupid arguement about randomness and complexity once and for all. Take a real good look: Those are metalic crystals of bismuth. Notice the order, the complexity, the regularity of the angles. By your logic, that means that God made them, which is flat-out wrong: any moron with a vat of water and a blowtorch and make them. But they *do* illustrate a core concept of evolution: how the imposition of a few simple rules to a random system can create complex order. These metalic crystals come from liquid bismuth, in which the atoms are unarranged and moving randomly. As it cools, they crystalize according to some simple rules for atomic bonding. These simple rules, imposed upon the randomness, can generate complex and orderly results, namely the crystals you see above. While mutation is random, natural selection most definitely is *not*. Selection acts like the atomic bonding rules, imposing order on randomness and resulting in what we percieve as a complex, ordered system. So basically, unless you claim that God directly and miraculously intervenes to guide the formation of every single crystal anywhere ever (even salt crystals I grow in a jar)(and thereby totally ignoring every aspect of materials science and chemistry), you must admit that your arguement is a baseless strawman. Mokele PS. Mods, please don't make the pics into URLs, at least until shinbits' inevitiable banning occurs, since it's clear that he won't confront data unless we shove his nose in it.