Skip to comments.Great Exaptations: Most Traits Emerge for No Crucial Reason, Scientists Find
Posted on 07/20/2013 4:15:21 PM PDT by SunkenCiv
Exactly how new traits emerge is a question that has long puzzled evolutionary biologists. While some adaptations develop to address a specific need, others (called "exaptations") develop as a by-product of another feature with minor or no function, and may acquire more or greater uses later...
How common such pre-adaptive traits are in relation to adaptive traits is unclear. Santa Fe Institute External Professor Andreas Wagner and colleague Aditya Barve, both evolutionary biologists at the University of Zurich, decided to get a systematic handle on how traits originate by studying all the chemical reactions taking place in an organism's metabolism...
They found that most metabolisms were viable on about five other carbon sources -- sugars, building blocks of DNA or RNA, or proteins -- that are naturally common but chemically distinct compounds. To be certain that viability on these other carbon sources wasn't a natural consequence of viability on glucose, they tested metabolisms starting with viability on 49 other carbon sources, and each time found that exaptations emerged allowing the metabolism to survive on any one of several other carbon sources alone...
By varying the number of reactions in a metabolic system, the team also found a relationship between the system's complexity (determined by number of reactions) and the extent of the exaptations, with larger networks having more of them.
The findings underscore the idea that traits we see now -- even complex ones, like color vision -- may have had neutral origins that sat latent for generations before spreading through populations, Wagner says...
If exaptations are pervasive in evolution, he adds, it becomes difficult to distinguish adaptation from exaptation, and it could change the way evolutionary biologists think about selective advantage as the primary driver of natural selection.
(Excerpt) Read more at sciencedaily.com ...
Feathers did not originate for flight but may have helped insulate or waterproof dinosaurs before helping birds fly. (Credit: © EcoView / Fotolia)
Ain’t life grand? We are products of chemistry and mutations. Happiness occurs between some people’s ears and not between the ears of others. I am lucky enough to have happiness occur. Granted, I do work at providing an environment where happiness flourishes.
If by “adaptations” they mean “mutations,” then logically they must always be random regardless of the needs of the creature. Just because you’re out at sea all the time, doesn’t mean your kids are going to develop gills.
What are the odds of developing a genetic Swiss Army Knife so dynamic that it overcomes the Law of Entropy and creates the most intelligent, adaptable being the universe knows?
The restatement of Darwinian Natural Selection adds “mutations arise at random” to the environmental (and sexual) selection process — but basically, only the random mutations lead to speciation; there’s no role that the ns hypothesis *can* play in speciation, it can only work as a method of extinction.
Add in the documented facts of mass extinction events caused by (for example) big rocks from space, and it’s easy to see why the Chicxulub impact and the Alvarez model is still being attacked by the “my state-paid professor said it, I believe it, that settles it” students ‘educated’ in the UK.
It would be wonderful if the writer of this article would have spent a little more time trying to get the science correct.
Evolutionary biologists are *NOT* trying to figure out how evolution occurs. They may be trying to work out tiny details, but the mechanisms are known. It is well-known that mutations are random, evolution proceeds by genetic drift, and speciation occurs when a population is split, causing two different groups that genetically drift in two directions and eventually become two different species.
Frankly, I'm disappointed that the editors of ScienceDaily didn't vet this article a little better. Scientific concepts can be simplified without making them inaccurate.
The relatively recent development of fair skinned homo sapiens living in Europe, and lactose digesting (milk consumption) enzymes in central Europe are prime examples. These mutations undoubtedly popped up occasionally long before they became useful to their owners. It was not until former Africans moved into Europe that they needed light skin to better use sun on the skin to produce vitamin D essential for good hip (reproductive) structure. Also, until homo sapiens began herding and milking cattle, there was no special utility to having lactose digesting enzymes. Once they had survival value, these genes proliferated rapidly by enhancing survival.
You have a provided an excellent example. Where I think it is a lot harder to comprehend the numbers working out on a completely random basis is in the origination of incredibly complex systems in species that did not have them resulting in an end state different from the one that provided the survival advantage along the way. So the feather mutation flourished because it provided warmth but that actually ended up leading to flight. And the numbers would seem more difficult with all the little bits and pieces that make up the eye but which until they come together to produce vision seem to have very little survival advantage.
Really? There is zero evidence of one species evolving into another distinct specie. There is evidence, plenty of it, of a family evolving but remaining very similar to the original specie of that family. If you look at bird skeletons you can clearly see the resemblance to dinosaurs. There is no crossover reptile / mammal species. It looks like mammals just "appeared" one day after reptiles and after marine gilled species.
The process is not quite as random as some people seem to think. The laws of physics put a very strong constraint on what is and is not possible. Vision is based on the fact that some chemicals absorb specific wavelengths of light. Even single-cell organisms have eyespots. Eyes have arisen many times, in many different forms.
Seriously? I'm interested in discussing science, not creationist anti-science. If you have verifiable, reliable documentation that all scientists that have ever existed are wrong, provide it--and I do not mean copy-paste from Answers in Genesis. Otherwise, I'm not interested.
Short Primer on Probability
Now we will look at the cumulative idea and see if that is a go or not. For Evolution to be true there has to be a large amount of cumulative organization of positive mutations. In fact Evolution says that all life came out of prior non-life. Darwins warm pond or the lightning charged primordial soup of other evolutionists. Could that really happen? What do statistics say?
The amateur evolutionist above thinks that four and a half billion years seems to be enough, but is it?
We will give him not the 4.6 billion years for life but the whole supposed age of the universe of 20 billion. We will even assume that ALL of the 20 billion years are good and that all the precursors to life are in some warm primordial soup (we will discuss this in the Biochemistry section below) somewhere just waiting to do their thing.
Lets talk briefly about probability which is a subset of Statistics. What is the chance if you toss a coin you get heads? Assuming the coin is equally weighted, and not a trick coin, it is 1/2. On a die the probability of rolling a six is 1/6. The probability of tossing a coin and getting heads and rolling a die and getting a six is 1/2 x 1/6 = 1/12. Now this doesnt mean that in twelve tosses and throws you will get simultaneously a head and a six, it means that if you throw long enough 1/12 of all throws will have both a head and a six.
Now let us get a little more complicated. Lets figure the odds or probability of randomly spelling the phrase the theory of evolution. There are 26 letters and one space possible adding to 27 possible selections. There are 20 letters in the phrase and 3 spaces. Therefore the odds, on the average, spell out the phrase correctly only once in 2723 outcomes! That is only one success in 8.3 quadrillion, quadrillion attempts or 8.3 x 1032. Now suppose chance uses a machine which removes, records and replaces all the letters randomly at the fantastic speed of one billion per microsecond (one quadrillion per second). On the average the phrase would happen once in 25 billion years by this method.
Whoops! We ran out of time just trying to randomly recombine correctly a 23 letter and space phrase. You see the probability multiplication rule is not so kind to the randomness of evolution thought.
But lets look at biological beginnings. You see in that warm pond or primal soup we just assume that there were amino acids there and we will assume that there were all the L type necessary for life. We will look later at Biochemistry and see it those assumptions are safe, but for now we will just assume them. One thing we will have to turn off is natural selection, because natural selection wont work here. We are just trying to polymerize a self replicating organic structure like a DNA or RNA molecule, and natural selection assumes that a good allele will be safe and a bad allele wont, and we dont have any good or bad alleles yet. We are just trying to get the genes now in the right sequence. If they are not in the right sequence they wont work and if they are, they will. And there is no way for evolution or natural selection or whatever other magic driver the evolutionists can come up with to know if the sequence is right until it replicates. There is no cumulative process here as a partially correct complex molecule wont work and would be discarded until one does.
The odds of forming a chain of 124 specifically sequenced proteins of 400 amino acid bases is 1 x 1064,489! Now that is just one complex molecule and life requires much, much more. Mycoplasma genitalium has the smallest known genome of the free living organisms, containing 482 genes comprising 580,000 bases. A human DNA molecule can contain three billion amino acid bases. That is not counting all the other enzymes, proteins, hormones and other life chemistry needed. These odds are utterly impossible and shows that evolution being the source of lifes beginning is not even remotely possible.
Fred Hoyle stated this: Two thousand different and very complex enzymes are required for a living organism to exist. And random shuffling processes could not form a single one of these even in 20 billion years. I dont know how long it is going to be before astronomers generally recognize that the arrangement of not even one of the many thousand of biopolymers (Life molecules) on which life depends could have been arrived at by natural processes here on earth.
Astronomers will have little difficulty in understanding this because they will be assured by biologists that it is not so; the biologists having been assured in their turn by others that it is not so. The others are groups of persons who believe, quite openly, in mathematical miracles.
They advocate the belief that, tucked away in nature outside of normal physics, there is a law which performs miracles (provided the miracles are in the aid of biology). The curious situation sits oddly on a profession that for long has been dedicated to coming up with logical explanations. . . The modern miracle workers are always found to be living in the twilight fringes of thermodynamics.
Fred Hoyle, The Big Bang in Astronomy, in New Scientist, November 19, 1981, pp 521-527
Why do eyespots develop and what is the environmental advantage of an eyespot? I am curious about this because the human eye is so complex in and of itself, but you also need the processing power of the brain to have it all come together. What's the value of a partial eye?
A single cell organism uses its eyespot to guide it towards light (where it can photosynthesize). This is a purely mechanical process, since they do not actually see. Light activates motor proteins that cause the flagellum to whip around, and the eyespot detects the direction with the highest light level, which activates other motor proteins that change the direction of movement.
Even in humans, not all light-sensing is mediated through the eye. We also have photoreactive chemicals in our skin. Tanning, for example, occurs as a result of light exposure.
Spiders and other creepy crawlers have tiny brains, and they do not process images much at all. Still, they respond to movement and levels of light. Despite their rudimentary vision, jumping spiders are pretty good at launching themselves unerringly towards their prey.
Other animals see far better than we do. For example, birds devote most of their brain to image processing, and they see orders of magnitude more detail than we. However, their eyes do not swivel in their heads--that is why they bob their heads when they walk.
Plants also respond to light through photoreactive chemicals. They have no vision whatsoever.
OK, the very first eyespots were on single cell organisms for photosenthesis. Would the simple eyespot distinguish between sunlight and moonlight? Do we have theories as to how they developed in predators? As the eye developed, the brain would have to develop as well so that it could process even rudimentary images, correct?
A simple eyespot probably does not detect moonlight. Light would have to have a certain minimum energy to interact with the photoreactive pigments in the eyespot. Also, the eyespot probably senses light centered around a specific wavelength.
The likely mechanism of the evolution of eyes has been pieced together by the examination of primitive eyes in current living species. Some species have light-sensitive patches of cells, while others have formed an indentation filled with light-sensitive cells. Because the indentation provides some protection to the light sensitive cells, the individuals with indented eye patches would tend to live longer and reproduce more. Over time (thousands of generations), the indentation becomes deeper and finally becomes a pit. A pit covered with translucent skin protects the light sensing cells better than an open pit. A lens would concentrate light, and probably developed from a thickening in the translucent eye skin. All of these eye variations currently exist. It is not necessary to have a brain to process rudimentary visual information--I'm pretty sure that scallops, with their hundreds of eyes, do not have a brain. In animals that have highly acute vision, the brain and eye probably became more complex simultaneously.
An interesting aside: I read about a man who was blind from birth, whose sight was restored by a novel kind of surgery when he was an adult. Because he had never had the kind of visual stimulation that infants and children get very early (while their brains are still malleable), he never learned to process the images. He could not see some optical illusions--like the ones where parallel lines appear slanted, he saw as parallel. And he could learn to recognize shapes and colors, but never learned to recognize faces. After spending most of his life blind, he continued to use non-visual clues to recognize people.