-
Asked by souveer to Amy, Drew, Julia, Kimberley, Sara on 17 Jun 2011. This question was also asked by cai192546, chocoholiclea, akyofori.
-
Drew Rae answered on 16 Jun 2011:
Hi Cai. Thats a question I’ve asked myself, and it isn’t an easy one to answer. Rather than give you a straight answer, I’ll describe a method you could use to think about it yourself and tell us what you conclude.
Darwinian evolution needs two elements:
1) It needs a source of new patterns (usually mutation from existing patterns)
2) It needs some source of selective pressure (if there were infinite resources, even sub-optimal patterns could survive) so that some patterns are more likely to survive than others.If we have these things, we expect to see evolution. So the first question is, do we have these things?
Evolution takes place over long time scales, so it’s hard to spot totally new mutations going from first appearance to being dominant in a population. Over shorter timescales though, you can see some gene expressions becoming more popular, and others becoming less popular.
So can we see this happening? Pick a human attribute that we could measure how common it was a couple of hundred years ago, and compare it to now. Do this a few times, because one example wouldn’t necessarily be representative. A lot of this will be influenced by lifestyle, which creates noise in our data, but you might be able to come to some conclusions.
-
-
Julia Griffen answered on 16 Jun 2011:
HI Souverr & Cai…
So drews given a thorough answer… but i have a question… What do you think we’d evolve into?
-
Amy MacQueen answered on 16 Jun 2011:
It’s a good question guys and quite complex to answer.
As Drew says we need mutation and selection – there are mutations happening but most of the ones we can see appear to be detrimental to our survival and manifest themselves in disease conditions which we try and treat. Some of these are passed on if the disease is not too serious to the next generation – but a lot of them are so detrimental that the individuals do not make it to adulthood and pass on their genetic variation. Thus these mutations are lost and do not influence the next generation.
There are, of course, bound to be lots of mutations that are masked to us just now because they do not have an obvious “phenotype” that we can see. These mutations do not really have a huge effect on us – either positive or negative – and will build up in our genomes until they do affect us. Then they could be selected for if they are useful in a given environment and the other people without it do not live long enough, or are not well enough in this new environment, to pass on their genetic information by having children.
There is then a third category of “positive mutations” which enhance us and give us a distinct advantage over our peers. But yet again these really only work when you have selection pressure e.g. because if in your culture wheat is poisonous to you and it has been passed down from generation to generation not to eat it you are unlikely to do so (even if by chance you have a mutation which allows you to do so)…only if no other foodstuff is available will you be forced into it and then have the advantage because you survive and everyone else is hungry.
What leads us into difficulties is the fact that most human communities in the world show care and concern for other individuals in the community and, unless you have a very severe mutation that impacts your health, the other mutations you may have are not really that big a deal anymore – especially in countries with good medical services and a social benefits system! So you could argue that selection pressure on humans (in most environments) no longer exists and therefore – unless we are forced into a particular extreme situation – we can all survive regardless of our genetic make-up.
Some people have decided that they want to create a “super race” and go around trying to form one – this then causes ethical and social problems and is enforced selection pressure – i.e. selective breeding, which is more to do with ideals rather than the environment.Also in some communities people have amazing abilities – like being able to hold their breath for a long time to catch fish deep under the sea – these people share the fish with those who can’t do this so they’re not dying out from selective pressure. Then it also brings up the question: are these abilities purely genetic? or trainable? is altruism a valid evolutionary concept? does it confer advantage to US to be kind? is evolution driven by the individual or the species as a whole? and why would we even want to survive? why does life want to exist – what is driving it? or does it just exist “because it can”? why is there something other than nothing?
Bet you wish you never asked – I find it really interesting though! 🙂
-
Kimberley Bryon answered on 16 Jun 2011:
I think that we are still evolving but at such a slow rate that we can’t really see it. As Drew and Amy have said we need a selection pressure. If there ever was a new disease that only some people with a specific mutation could survive then that could cause humans to evolve with that mutation.
Examples of diseases with selection pressure that I can think of off the top of my head are sickle cell anaemia as it gives some protection from malaria and the cystic fibrosis gene might protect against TB if you only get one copy. Because these genes give protection from some diseases they are maintained in the population. If malaria was wiped out then less people would have sickle cell anaemia or it might die out all together, over time.
-
Sara Imari Walker answered on 17 Jun 2011:
Hey great question!! You all are really on top of your game. Sorry to enter the discussion a little late – this time zone difference is tough sometimes 😉
Amy has given such a great and thorough answer. Its really inspiring! I share her enthusiasm for thinking about this question on a deeper level, especially since it has huge ramifications for our understanding of complex and intelligent life (like us) on other planets as well as our own. Since Amy, Drew, and Kimberley did such a great job covering what might be going on with Darwinian evolution of modern humans I am going to step out of the box a little and talk about other kinds of evolution. There are a lot of arguments out there for humans no longer being subject to Darwinian evolution based on selection of the fittest (i.e. no selection pressure as described by my science mates here). That may be true, and if it is true, it is a result of our technological advance more than anything else. Technology allows us to defy biological law in some sense – but it also allows us to use it to our advantage with things like genetic engineering etc. That’s all well and good, but what interests me is that humanity may now be past evolution by Darwin and on to a stage of cultural evolution that is very different. Well what do I mean ‘cultural evolution’?
In our global society humans are able to survive and reproduce in part because of habits, know-how and technology that are generated and maintained through social learning. To go back to the example in your question, one thing we teach our children is how we grasp the environment and harness it to our advantage! This is exactly what prevents selection from acting – we teach our children and neighbors things that will help them survive (including sharing fish 😉 ). Information is passed from person to person as a learned process rather than an inherited one. That is a completely non-Darwinian (remember Darwin talked about heritable traits) process! So yes, we are definitely still evolving, but maybe just not in a way you might first expect. We have a lot to learn about this yet: remember human culture is only a few thousand years old (with real technology being even much much younger than that), Darwinian evolution has ruled this planet for over 3.5 billion years! We are in new territory here!
Comments