Evolution - Reality and Misconceptions
Discussion
Toltec said:
otolith said:
OK, but that is altering the expression of a gene during an individual's life. It isn't altering their genome. They will still pass the same sequence they were born with to their offspring.
This kind of thing?https://www.newscientist.com/article/2127103-squid...
It doesn't really matter what you're born with if you can edit it on the fly or it can be changed by external factors.
And as an aside can anyone answer this? I know we've mapped the human genome and presumably repeated this loads of times but until we've mapped All the humans genomes we don't really know what we're dealing with, do we? They may well walk among us.
FredClogs said:
I know we've mapped the human genome and presumably repeated this loads of times but until we've mapped All the humans genomes we don't really know what we're dealing with, do we? They may well walk among us.
The original human genome project was a mosaic taken from multiple individuals. Scientists routinely sequence hundreds of genes from many thousands of individuals for research and genetics tests worldwide. Whilst this isn't as complete as doing a full genome sequence it provides a good indication of how well conserved a pretty good cross section of genes are across the population. When I worked in research we would routinely test hundreds of motor neuron disease patients looking for single nucleotide polymorphisms compared to healthy individuals. Most genes were pretty consistent across individuals, most mutations were silent.
It's now apparent that we're not a very diverse species. Two Norwegians will have about the same diversity in their genome as a Norwegian and someone from Africa. The human species probably came very close to extinction not that long ago (50-70000 years ago). We're very in-bred, even those of us not from Norfolk
otolith said:
Toltec said:
otolith said:
OK, but that is altering the expression of a gene during an individual's life. It isn't altering their genome. They will still pass the same sequence they were born with to their offspring.
This kind of thing?https://www.newscientist.com/article/2127103-squid...
If you're really interested in this, I'd highly recommend reading Death at a Distance by Bingham and another. It's a fascinating explanation of why humans ended up as humans and the evolutionary/genetic evidence to support the theory.
The basic premise is that humans are the way they are because they cooperate in their groups and the scale of the groups is dictated by the evolution of our ability to project force at a distance. The argument is compelling.
Obviously evolution is wider than humans, but it covers all the basics in a lot of detail and is a fascinating read in it's own right.
The basic premise is that humans are the way they are because they cooperate in their groups and the scale of the groups is dictated by the evolution of our ability to project force at a distance. The argument is compelling.
Obviously evolution is wider than humans, but it covers all the basics in a lot of detail and is a fascinating read in it's own right.
otolith said:
OK, but that is altering the expression of a gene during an individual's life. It isn't altering their genome. They will still pass the same sequence they were born with to their offspring.
Not quite - see epigenetics. Things can happen to you that do affect gene expression in your children.Nessa Carey's book "The Epigenetics Revolution" is quite readable and very interesting, with lots of examples.
Nimby said:
otolith said:
OK, but that is altering the expression of a gene during an individual's life. It isn't altering their genome. They will still pass the same sequence they were born with to their offspring.
Not quite - see epigenetics. Things can happen to you that do affect gene expression in your children.Nessa Carey's book "The Epigenetics Revolution" is quite readable and very interesting, with lots of examples.
otolith said:
Epigenetic effects don’t alter the genome - that’s the point.
The Wikipedia article says "The term also refers to the changes themselves: functionally relevant changes to the genome that do not involve a change in the nucleotide sequence.The genome is the DNA sequence (AGCT) and heritable methylation / histone modification.
TwigtheWonderkid said:
I think the current must read book for the latest on evolution is The Greatest Show On Earth by Richard Dawkins. And for those who dislike Dawkins, it's written in his capacity as one of the world's leading evolutionary biologists as opposed to one of the world's leading atheists.
It's a really great book.
Are you referring to this Dawkins? It's a really great book.
https://www.youtube.com/watch?v=Pckg3Kud8_A
otolith said:
Sure, but the context was speciation and punctuated equilibria and I just don't see heritable differential expression being particularly relevant here.
I think I understand but I'm watching Ben Fogle trying to get up Everest on telly, and as ever with these tales the really interesting thing is the way the Sherpa are able to cope better with the altitude. A small segregated collection of peoples adapted to live on top of the world through an undeniable physical difference to "normal" humans. They may share the same genome as me but they don't use it in the same way. I may not be right but I suspect that were some catastrophic environmental event to befall humanity the things that would help us evolve beyond it or possibly speciate there after would not be random mutations but something that is already in us.
Interesting story behind the genetic adaptation of Tibetans;
http://www.sciencemag.org/news/2014/07/tibetans-in...
A radical change in our selection pressures would indeed be likely to result in a change in the frequencies of existing genes. As for new mutations - I should think people are born all the time with mutations which are neutral or maladaptive in our current environment but which would be an advantage were conditions different. We are currently quite maladapted to our historically anomalous excess of food. It doesn’t tend to kill us during our reproductive years, but I dare say that given long enough with current conditions we’d see sexual selection for people who don’t turn into hippos given access to unlimited calories.
http://www.sciencemag.org/news/2014/07/tibetans-in...
A radical change in our selection pressures would indeed be likely to result in a change in the frequencies of existing genes. As for new mutations - I should think people are born all the time with mutations which are neutral or maladaptive in our current environment but which would be an advantage were conditions different. We are currently quite maladapted to our historically anomalous excess of food. It doesn’t tend to kill us during our reproductive years, but I dare say that given long enough with current conditions we’d see sexual selection for people who don’t turn into hippos given access to unlimited calories.
In terms of misconceptions, with DNA expression, I am always amazed about people's ignorance of it. Whilst it's quite popular in the media, it isn't a new field of biology, they teach it to highschool children.
I mean, there's quite a contrast between a catterpillar and a butterfly, but they share 100% of their DNA. It gives some indication of the significance of it.
I mean, there's quite a contrast between a catterpillar and a butterfly, but they share 100% of their DNA. It gives some indication of the significance of it.
Edited by Prof Prolapse on Friday 31st August 10:29
FredClogs said:
I may not be right but I suspect that were some catastrophic environmental event to befall humanity the things that would help us evolve beyond it or possibly speciate there after would not be random mutations but something that is already in us.
Most changes we see is due to genes which already exist. Selective breeding of dogs is a great example. To selectively breed something as diverse from it's shared ancestor as a s
tzu takes many years, perhaps hundreds or even thousands, but in evolutionary terms that is simply not enough time to produce a new phenotype solely from random mutation. Evolution takes millions of years. You're just selecting from the existing gene pool. Same goes for humans. In your scenario you would be selecting from the existing gene pool, certain stresses may increase the expression of certain genes (ala the mountain climber scenario) but ultimately any new genes brought about by random mutation and subsequent natural selection, could take millions of years. Whatever creature benefitted, would perhas not even be considered human. Not in the Homo Sapiens sense anyway.
Prof Prolapse said:
Whatever creature benefitted, would perhas not even be considered human. Not in the Homo Sapiens sense anyway.
Here's an arresting thought. The sun is about half way through it's life. In about 5 billion years it will undergo a supernova. Given what Earth has gone through in the last 4.5 billion years there's every reason to believe that Earth will still sustain life. However, the creatures that witness the sun exploding will probably be as different to us as we are to the first single celled organisms that appeared 3.5 billion years ago. Another related interesting thought. Dawkins proposed a 3 dimensional evolutionary space where you could imagine every permutation of every gene that could ever exist. Within this 3 dimensional space there are islands of interconnected space where functional organisms exist. He imagined that only a tiny tiny percentage of the potential genetic space had ever been explored in the last 3.5 billion years. I wonder how much of that space will be explored by the time the "Earth Experiment" reaches a conclusion in the next 5 billion years?
Another interesting aside, I wonder why in all the time evolution has had, no creature that we know of has evolved ways of exploiting the electromagnetic spectrum (other than UV, visible light and IR). Why are there no creatures that can naturally (without technology) communicate via radio waves for example.
Prof Prolapse said:
Most changes we see is due to genes which already exist. Selective breeding of dogs is a great example. To selectively breed something as diverse from it's shared ancestor as a stzu takes many years, perhaps hundreds or even thousands, but in evolutionary terms that is simply not enough time to produce a new phenotype solely from random mutation. Evolution takes millions of years. You're just selecting from the existing gene pool.
I think dogs are actually a special case. Selective breeding of Horses, Sheep Cattle etc hasn't produced nearly as much variation. tzu takes many years, perhaps hundreds or even thousands, but in evolutionary terms that is simply not enough time to produce a new phenotype solely from random mutation. Evolution takes millions of years. You're just selecting from the existing gene pool. Dr Jekyll said:
I think dogs are actually a special case. Selective breeding of Horses, Sheep Cattle etc hasn't produced nearly as much variation.
How would you know though?With notable examples, for the most part agricultural breeding is taken with an aim to increase efficiency. It says nothing for the potential diversity of phenotypes in the gene pool. By contrast breeding of dogs has been traditionally for both more diverse utility, and even simply for aesthetics, or diversity itself.
Prof Prolapse said:
How would you know though?
With notable examples, for the most part agricultural breeding is taken with an aim to increase efficiency. It says nothing for the potential diversity of phenotypes in the gene pool. By contrast breeding of dogs has been traditionally for both more diverse utility, and even simply for aesthetics, or diversity itself.
That’s certainly part of it. But look at the differences between a greyhound and a wolf as opposed to between a wild horse and a racehorseWith notable examples, for the most part agricultural breeding is taken with an aim to increase efficiency. It says nothing for the potential diversity of phenotypes in the gene pool. By contrast breeding of dogs has been traditionally for both more diverse utility, and even simply for aesthetics, or diversity itself.
They're diverse for sure, but your point was that you believe they are "special" implying they're in some way exceptional in that regard.
My point remains that very few, if any, species have been similarly selected for diversity in the same way that dogs have. So how could you know it wasn't exceptional, it could be very common.
I mean for all we know you can selectively breed hippos to be four inches high, fly, and glow in the dark, there's no real way of quanitfying and comparing equivalence here.
I would be curious to what extent you could speculate on diversity from a genome however. I would like a glow in the dark hippo.
My point remains that very few, if any, species have been similarly selected for diversity in the same way that dogs have. So how could you know it wasn't exceptional, it could be very common.
I mean for all we know you can selectively breed hippos to be four inches high, fly, and glow in the dark, there's no real way of quanitfying and comparing equivalence here.
I would be curious to what extent you could speculate on diversity from a genome however. I would like a glow in the dark hippo.
Edited by Prof Prolapse on Friday 31st August 12:01
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