http://www.dictionary.com defines evolution as any process of formation or growth; development: the evolution of a language; the evolution of the airplane. So if we evolved from apes, why did we lose one chromosome?
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http://www.dictionary.com defines evolution as any process of formation or growth; development: the evolution of a language; the evolution of the airplane. So if we evolved from apes, why did we lose one chromosome?
Biological ecvolution and cultural evolution are two different processes. The term evolution needs to be used carefully, it has been eroded in a sense, much like the word organic.
Naturally, biological evolution says nothing about a need to gain chromosomes, as that would be at odds with the process which is basically random changes, allowing some percentage (of offspring) to survive a changing environment.
I don't have the technical knowledge to answer, or even confirm the factual accuracy of, the above question, but I have enough general knowledge to remember it is a basic error to state that we "evolved from apes" when one should say that humans and apes have a common ancestor.Quote:
Originally Posted by WVBIG
WVBIG, the technical definition of biological evolution is a change in gene frequencies over time. Any change of any kind by any mechanism. As long as the offspring are not 100% identical to the parents, evolution is happening.
Natural selection is one of several mechanisms by which evolution can happen, and it is natural selection that leads to adaptations to the environment. Losing traits can be just as adaptive as gaining them. For example, animals that live deep in caves often lose skin pigmentation and their eyes. Why? Generating eyes and generating skin pigment isn't free, it takes up energy. But these animals now live in an environment where there is no benefit to eyes or skin pigment, and that energy could be better spent elsewhere.
Sorry to nitpick, free radical, but we are talking about definitions here. Evolution is not in itself a random process. Some of the mechanisms of evolution, the mechanisms of change, are random (mutation, drift, etc), but some of them are not, some of them are directional (natural selection).Quote:
Naturally, biological evolution says nothing about a need to gain chromosomes, as that would be at odds with the process which is basically random changes, allowing some percentage (of offspring) to survive a changing environment.
It's like what Halliday said, apes and humans evolved from a common ancestor (most likely with the same amount of chromosomes as us), which means that they could have gained a chromosome. Humans could have lost a chromosome along the way, but the apes gaining seems more likely, since ancient species like ferns apparently have dozens.
Of course, technically speaking, humans are apes, but that's not really relevant
Humans have one less chromosome because two of our ancestral chromosomes fused together into one. Thus we didn't actually lose one, two just joined together.
1. Losing something is not necessarily regression.
2. Evolution can happen in multitude of directions. You don't always go from less complicated to more complicated.
The dictionary definition refers to the original and very general meaning of the word. There are various mechanisms colloquially referred to as "evolution" in which the word simply means "change over time", not necessarily meaning growth. Stellar evolution refers to the changes that a star undergoes over its lifetime, which may include growth or catastrophic loss of mass. Similarly, biological evolution just refers to the changes we have seen in organisms over time.Quote:
Originally Posted by WVBIG
The chromosome was not lost, two chromosomes fused to form one longer chromosome. Even if it had been lost, this would not contradict our understanding of evolution as change.Quote:
Originally Posted by WVBIG
Here is a great video from one of Ken Millers presentations that explains exactly what occurred.
http://www.youtube.com/watch?v=zi8FfMBYCkk
Now that I reas the posts I realize this might be a bit redundent.Quote:
Originally Posted by WVBIG
We didn't lose it (that would be fatal), two chromosomes fused together, this is shown by finding two centromeres on our chromosome 2 (there usually is only one) and finding telomeres (usually found on the ends of a chromosome) at the center of our chromosome 2.
Also reversion is possible in evolution, as shown by the loss of function of many genes involved in scent, which work in mice but are in inactive form in us.
http://www.evolutionpages.com/chromo...htm#References
Are humans the optimal species on the planet? Darwinian idea is controversial for me not because it opposes creationism, but because it underestimates the chance. For example, creatures with two pairs of arms should become more intelligent than creatures with just one pair. They would be forced to process and use tools faster in order to stay in competition against each other, and their brains would have to adapt accordingly. No such creatures materialized at the stage where the transition to primates occurred, but if they did, everything else being equal, this additional pair of hands would give them an edge to defeat other species and increase their intelligence competing among themselves.
Optimal according to what standard? We are among the most widespread species and one of the most numerous mammals. We do have the most general intelligence of any known animals. But when it comes to specific tasks and traits, other organisms could be considered more optimal.Quote:
Originally Posted by bongobay
It may have started out as Darwin's idea but modern evolutionary theory has changed considerably since Darwin's time. It is not a controversial idea in science as evolution is one of the most robustly supported explanatory frameworks in the history of science. But what do you mean, underestimates the chance? Chance of what?Quote:
Darwinian idea is controversial for me not because it opposes creationism, but because it underestimates the chance.
Why should they? Insects have six pairs of limbs total and no one insect is smarter than a single human. Octopi have four pairs of limbs and though they are among the smartest invertebrates they are not smarter than humans either.Quote:
For example, creatures with two pairs of arms should become more intelligent than creatures with just one pair.
That's assuming they use tools at all. Most animals don't. And speedier use does not necessarily mean better competitor. Speed only helps you as long as you can still do the job well, and sometimes those two do not go hand in hand. Sometimes you have to choose one or the other, speed (quantity) or quality.Quote:
They would be forced to process and use tools faster in order to stay in competition against each other, and their brains would have to adapt accordingly.
Not necessarily. Just because you have more motor control doesn't necessarily mean you have more general intelligence, as evidenced by my examples of animals with more limbs than humans but that are certainly not as smart.Quote:
No such creatures materialized at the stage where the transition to primates occurred, but if they did, everything else being equal, this additional pair of hands would give them an edge to defeat other species and increase their intelligence competing among themselves.
I said “everything being equal.” I know that some creatures have more than a pair of functional extensions, some have dozens. And this was only an example of one set of characteristics that may have helped humanoid, but not necessary humanoid, creatures to outcompete humans. Because humans rule the planet does not mean that humans are the absolute, final complex organism that could have ever evolved. When primates evolved from mammals, there was only one branch of primates, one individual at the initial stage. Then, with time, hundreds, already different from each other creatures materialized. And one of them became human, because it did so only by chance, unless you want to say that humans evolved from the fittest of them. If so, there is no proof of that.
paralith said "Optimal according to what standard? We are among the most widespread species and one of the most numerous mammals. We do have the most general intelligence of any known animals. But when it comes to specific tasks and traits, other organisms could be considered more optimal"
I agree. Supposedly, cockroaches would survive nuclear war. Does that mean they are optimal to humans?
In the event of a world-wide nuclear holocaust, yes.
You could similarly ask why the biplane evolved into a plane with a single pair of wings. Equally valid question.Quote:
Originally Posted by WVBIG
Drosophila lost a lot more than a chromosome. It streamlined its genome.
It evolved.