Is it a coincidence that of all the mutations that have occured to humans, not one has been beneficial overall

Question

eg. Haemoglobin transports oxygen. There have been over forty other mutated versions of haemoglobin that carry oxygen, yet not one of them actually transports haemoglobin better than the original, normal haemoglobin.

Answer 1

Actually, you're a little bit off on this one, Gentle Asker.

You may wish to search the site below for the whole phrases, quotes and all, of "human brain size", "genetic mutations", and "human diet".

http://www.sciencenews.org/

The point of it is that while civilization may have slowed down human evolution significantly, it hasn't utterly stopped it.  At least two mutations have occurred, at least 14,000 years ago, and one as recently as 5,000 years ago, that both increase human brain size.  One such mutation coincided with the use of polished stone tools and villages for the first time, while the other could be said to closely correlate to the beginning of *literate* civilization.

And....tolerances to certain sugars in adult humans, such as lactose (milk sugars) and mannose (present in certain tree nuts), have also came about by recent mutation as well.

Now....search that site above, again, this time for the phrases, quotes and all, of "malaria resistance" and "sickle-cell anemia".  Point of it is, yes, even the blood changes too, though changing that is more of a mixed blessing/curse than anything...

I hope this was helpful.  ^_^  Thanks for your time!  

Answer 2

Pale skin.  Useful for vitamin D synthesis in northern European climates.

Blue eyes.  Useful for making northern European babes look really hot.

Blond hair.  See blue eyes above.

Oh yeah.  Your precision grip is different than that of the other apes, thanks to mutations.  You're better at knapping stone than they are.  Not that they care.  You care because of your mutant enormous brain.

Answer 3

Yeah my mutant abilities benefit no one but me!! =()

Answer 4

I'm sorry that I didn't see this earlier.

What makes you think that "normal" haemoglobin is the original? There are several types of haemoglobin which comprise "normal". There is HbA, about 97-98%, HbA2, about 1-3%, and HbF (foetal Hb) about 0.5-1%. In foetuses and newborns up to about 6 months old, the HbF percentage is higher, before tapering off. It has a higher affinity to oxygen than HbA, so at the placenta, oxygen moves from HbA to HbF, and from mother to foetus.

The question is - why does HbA2 exist? It performs no function other than carry oxygen, and causes no problems if absent entirely. The answer lies in the fact that it is probably the original haemoglobin, with a mutation causing HbA to arise.

So, in answer to your question, clearly a beneficial mutation had occurred, one which gave rise to normal adult haemoglobin (HbA), and eventually led to the near complete replacement of the slightly inferior HbA2.

.

Answer 5

You are ignoring the plain and simple fact that there is no "normal" hemoglobin.  In human blood, the normal composition includes several percent of hemoglobin A2 composed of two alpha chains (the same as hemoglobin A), and two delta chains (where hemoglobin A has beta chains).  These are the result of hundreds of millions of years of fine tuning by evolution.  Both are functional molecules  It is hard to improve on a system that has been optimized by time, and the similarities between the beta and delta chains show a common descent

The function of hemoglobin is characterized by a moderate affinity for oxygen -- the capacity to bind and release.  Both increased and decreased affinity for oxygen disrupt the balance, so there is no simple direction for improvement.

Where is the selective pressure for an improved hemoglobin?  You will find increased myoglobin, rather than hemoglobin, increases the diving  capacity in mammals.  Further, hemoglobin is not a protein that acts on its own.  A variety of systems support hemoglobin, so in the absence of a selective pressure to change the function hemoglobin will be unlikely to undergo significant change.

Further, there are far more than 40 variant hemoglobin alleles in disease.  Most were detected because they produce symptoms, but more are found because they produce laboratory anomalies.  How would you even characterize an improved hemoglobin?  How many people fail to have children because they have ordinary hemoglobin not up to the task of survival?  It is not "coincidence" -- it is observer bias.

Lastly, observations of beneficial mutations in rodent hemoglobin have been observed.

Answer 6

Mutations are almost always bad, especially in highly evolved species like humans. If you plan on using this argument to combat evolution, don't. Mutations don't drive evolution, natural selection and time does.

Answer 7

I really like Bradley's and novangelis' answers.  

But let me add two more angles:

First, all we can talk about are mutations that we have *NOTICED*.   Chances are these are the mutations that are big enough to be very harmful.  Mutations that are slightly harmful, neutral, or slightly beneficial are very difficult to observe ... but we have examples of them anyway.  Large mutations (involving a lot of base-pair changes) that are also beneficial are *extremely* rare ... beneficial mutations are usually small improvements that would be very difficult to observe.

Second, there is something called the "fitness landscape".   By whatever path in evolution, we have arrived at a particular set of hemoglobin variants.  Natural selection has left us with pretty much the best ones along this pathway.   But that is NOT to say that a radically different design of the hemoglobin molecule might be *far* better then any we currently have.  

But there is no way to get those molecules via incremental mutations on our current hemoglobin variants without those intermediate stages being *LESS* efficient ... and so there is no way that natural selection can ever take us to those vastly superior molecules.

If anything it demonstrates why evolution-by-natural-selection is a much better explanation for the particular molecules we are woking with than "intelligent design."   An intelligent designer could easily find a much more efficient molecule ... it could even be another oxygen binder besides hemoglobin altogether, such as myoglobin or erythrocurorin found in earthworms.   But since evolution works by small incremental improvements selected by natural selection, not wholesale "design" of the optimal system from scratch ... we end up with the features and proteins that we have today.