The Robin on my front lawn is bipedal, but I ain’t seen him use a cigarette lighter, lately.
T Rex could, though. That’s why he’s extinct–too many ciggies.
I don’t think that is true. With two slightly different species competing for the same resource, the more efficient species is going to win out. Given millions of years, even mild advantages can be the difference between extinction and survival. Additionally, simple mate selection can make some characteristics dissappear very quickly.
Many of the genes that we consider to be detrimental in humans may have positive benefits that we haven’t found yet. The most obvious example is sickle cell anemia, which with two copies causes a problem but with one copy makes one immune to malaria.
Terrestrial vertebrates evolved from lobe-finned fish, which just happened to have had four lobed fins that evolved into limbs. All tetrapods are descended from that same ancestor some 350M years ago. It’s certainly possible that fish with more than 4 lobed fins could have evolved, in which case it’s certainly possible that terrestrial vertebrates with more than 4 limbs could have evolved. Four might be optimal in some way, but 6 or 8 might well prove optimal in some other way.
Is somebody making the argument that all bipedal animals are intelligent?
No. Genes can “die out” due to simple genetic drift.
Yes. Let’s remember that, in humans, non-coding DNA makes up about 80 - 90% of the our genome. Any mutation in the non-coding sections is most likely going to be neutral.
Unlikely that they would survive over time. Unless they also confer some additional advantage, they will disappear. But remember, they have to be detrimental to reproduction. Just being detrimental to survival isn’t enough.
I thought the Moties’ asymmetry is supposed to be understood as arising out of genetic engineering the Moties had performed on themselves at some point many many cycles ago. Hence you still have four-armed porter castes, and the closely related little Watchmakers. Is that not the whole point of the sequence in The Gripping Hand at the Blaine Institute where they’re talking about symmetry?
We agree then. You can take the position that it was by chance that we evolved from tetrapods, or you can believe there was some evolutionary advantage to 4 limbs. I choose the latter.
Since non-coding DNA has no effect on whether something is humanoid or not I don’t see the relevance.
For neutral mutations I would guess that the probability of survival is around 50%. For less advantageous mutations I would guess that the survival rate does not immediately drop to 0%.
Remember, though, this is GQ. Unless you have some evidence that it was the latter, then it’s just your opinion. The original point you made, and which I was responding to was this: “I think there may be an evolutionary reason for this.” Without any compelling argument one way or another, the simpler explanation is that it just happened that way by chance.
Because people are jumping all over the place in this thread-- one minute talking about humans and the next minute making sweeping statements about genetics and evolution in general.
Which is why I underlined “over time” in that post. I clearly was not talking about something that happened “immediately”.
Meet my friend, the “evolutionary constraint”. Not everything that could evolve in theory can evolve in practice. Terrestrial vertebrates evolved from a common ancestor, which had a specific body plan. That body plan happens to be very conservative; even though we find quite a bit of variety in the form of the four limbs, we still have only four limbs. Some groups have reduced that number, but none have increased it. That would imply that there is a good reason that it can’t happen. Most likely, it’s a result of Hox (aka Homeobox) genes; these gene suites are master developmental genes, and mucking with them, even a little, can have drastic effects for the developing embryo. As such, there isn’t as much room for variation in those genes as there are in others. Even in some of the peripheral Hox genes, such as those that control phalangeal development and growth, we only see a reduction in the number of phalanges, never an increase (at least not since the days of 8-9 phalanges in our very early ancestors).
And even in the case of reductions, it tends to be that the genes are simply turned off (i.e., the expression of those genes has been altered, but not necessarily the genes themsleves), not actually eliminated. Thus, we still find the occassional three-toed horse, or whale with vestigial hind limbs.
Because of our particular body-plan, we will most likely never gain limbs or even digits, regardless how useful they might be simply because the required mutations would be vast; we’d basically have to shift body plans, and that just doesn’t happen.
The key in that statement is “I think”. I think this because my experience as a chemist suggests that things tend to move through the easiest pathway. As I have mentioned before in this thread, we know very little about how evolution happens. This thread has been almost entirely conjecture.
I don’t know what sweeping statements you are refering to. I have given my opinion on how things worked. Many people have not liked what I have to say.
I think you are misunderstanding “immediately”. I meant that mutations that lead to only mildly detrimental attributes would survive nearly indefinitely. On that point, I think we dissagree.
No, somebody suggested it promoted tool use, & I refute the notion.
But evolution isn’t chemistry. It involves chemsitry just as it does physics, but that doesn’t make arguments based on the second law of thermodynamics relevant, nor does it make arguments based on chemical principles relevant.
We know that evolution doesn’t move through the easiest pathway, it moves through whatever pathway promotes reproduction for the individual regardless of how easy or hard that is. Bipedalism in humans isn’t easier in any sense than walking on the knuckles, nonetheless it evolved. that’s because because despite being more energetically expensive and risking spinal injury and making birth difficult and a multitude of other difficulties it conferred benefits that aided reproduction. Nothing to do with being easy thermodynamically or chmically or even physiologically. Purely and entirely based on reproductive rates.
I hope everyone disagrees because it’s not true. Once you declare that something is evolutionarily detrimental then you have also by definition said that it will be eliminated given sufficient time. If it won’t be eliminated given sufficient time then it isn’t detrimental, not even mildly.
I think your problem may be that the term “mildly detrimental” is almost meaningless in a discussion concerning evolution. Either a mutaion decreases reproductive succes or it does not. Some mutations will have a less evere effect on reproductive success, which is the only possible interpretation of “mildly detrimental” that make sany sense.
But if that is the sense that you mean then the statement is out-and-out incorrect. Mutations that only mildly affect reporductive success can’t survive indefinitely because by definition individuals that carry them have a decreased reproductive rate compared to the general population. Doesn’t matter if they are only eliminated with 0.00000001% greater frequency than the general population, the fact that they are elminated at a greater rate means the mutation must vanish.
Of course so do some apes and monkeys and they aren’t really bipedal.
So do otters, dogs and caddisflies. That totally misses the point.
The point is that there are countless bipedal animals on this planet that have never, ever been observed to use a tool, and a handful of species that have.
There are also countless quadripledal, hexipedal and octipedal creatures on this planet that have never, ever been observed to use a tool, and a handful of species that have.
There is no evidence whatsoever that bipedal animals are more prone to tool use than quadripedal or hexipedal or octipedal. Anyone claiming that bipedlaism promotes tool use neede to explain this observation before there claim can be taken seriously. If bipedalism promotes tool use then why are extant bipedal species no more likely to use tools than quadripedadal, hexipedal or octipedal species?
OK, but again… unless there is some reason to think that, then I don’t find the argument very convincing. At any rate, we don’t really know why the first lobe finned fish had 4 lobed fins as opposed to more. Maybe it’s just that it helps to have two in front and two in back and having more isn’t of much help. But the reason all land vertebrates have 4 limbs is because some fish a long time ago had 4 lobed fins.
Here’s an example, from one of your posts:
That’s a general statement about evolution and genetics, not about what makes a human a human. It is one that I believe is correct, but it is a very general statement nonetheless. Nothing wrong with that, in the same way there was nothing wrong with my statement about non-coding DNA.
Do you have a cite for that claim? Because, as I read it, it contradicts one of the fundamental tenets of the theory of evolution by natural selection. As I noted earlier, I’m reading “detrimental” to mean detrimental to reproductive success. If you simply mean that a mutation that is detrimental to something like life span, then you might be correct-- it might hang around for a long time, but whether it “would” do so is hard to say without knowing the specifics of that mutation.
I think the odds are incalculable.
Literally.
Well, duh.
Well, if it’s so obvious, why is there two pages of pointless ramblings?
Any attempt to calculate the odds is just so much mental masturbation, seeing as there is no way to prove any hypotheses at this time.
'Cause “mental masturbation” is both fun and keeps you in practice for the real thing. 
Seriously, the o.p.'s question was answered, seconded, and repeated in the first dozen or so posts, and the bulk of the remainder of the thread has gone onto this rather odd tangent about bipedalism and whether it does or does not promote/allow/essential to tool use, plus some kind of random, unstructured claims about thermodynamics and chemical equilibria, which has served to demonstrate that applying simplistic analogies don’t hold up well to a complex phenomena like evolution.
Regarding the biped/quadraped issue, it is, as the sage Darwin’s Finch points out, a mistake to think that the process of evolution explores all possible pathways. Why do spiders and other arachnids have eight legs, while most insects have only six legs, and mammals and reptiles have four extant or deprecated limbs? There’s no especially good reason that any of these numbers have to be thus (though having an even number of limbs is dictated by symmetry), and only in the case of aves can we even make a reasonable claim that parsimony demands the absolute minimum. An entire class of reptiles certainly gets by having dispensed with legs at all, and the cephalopods seem to have far more than any reasonable creature needs (and live fine should they lose two or three).
With natural selection there’s no planning ahead, or running a trade study to see if 13, 17, or 23 limbs will work out better than two; you start with the form you have and modify from thus, and the more complex form your initial specimen has the harder it is to make gradual modification that still fit in the overall scheme, hence why the finches of Galapagos, while being speciated by their adaptations to subsist on various niche food sources, show a common form rather than the diversity seen in mainland birds. Intelligent life evolving on another planet would likely–to a point of certainty–take different paths even if faced with the same gross evolutionary pressures, and the end result may be very different; instead of a savannah-hiking mammal-like biped, it might well be an litoral-dwelling quadralobe, or a social birdlike scavenger/predator, or a furry forest-and-praire-dwelling omnivore. It’s likely that it would even be something far different from any of our terrestrial life classifications. To say that the biped for is innately superior or even necessary to the development of higher intelligence and tool use is a blindly homo-centric view, unsupported by either reason or a useful body of data.
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