Mutation rate of early life forms

[MirceaKitsune]

Articles on the matter explain how everything started out with a bacteria that evolved into all the complex life forms we know today, during the course of millions of years. But one thing which hasn't been described is how frequently and to what extent a newborn had to experience mutations in order to evolve.

 

I got curious because I noticed that at this day, few large creatures experience any visible mutations... except of course traits like face shape, fur color, etc. Almost as if humans and most animals people encounter stopped evolving... or rather the process got too slow to even notice. I'm curious since this would help better understand how fast life started diversifying, soon after it got started.

 

How many mutations per newborn would have early forms had, and to what frequency and extent? And together with that, how long would have they lived and how frequently would have they reproduced? Why is it that large animals these days barely have offspring with visible mutations, whereas at some point this should have been at least somewhat more common?

[chadn737]

I find the premise flawed. Define a "visible mutation". For one thing, many mutations/alleles are probably quantitative in effect, thus altering a phenotype in a subtle way. For instance, a mutation that would say reduce or increase height by 2% would not be so noticeable or selected on strongly. As such, there can be many "mutants" walking around that go unnoticed due to the subtlety of difference.

 

There actually substantial numbers of de novo mutations in every individual human,

[Delta1212]

Articles on the matter explain how everything started out with a bacteria that evolved into all the complex life forms we know today, during the course of millions of years. But one thing which hasn't been described is how frequently and to what extent a newborn had to experience mutations in order to evolve.

 

I got curious because I noticed that at this day, few large creatures experience any visible mutations... except of course traits like face shape, fur color, etc. Almost as if humans and most animals people encounter stopped evolving... or rather the process got too slow to even notice. I'm curious since this would help better understand how fast life started diversifying, soon after it got started.

 

How many mutations per newborn would have early forms had, and to what frequency and extent? And together with that, how long would have they lived and how frequently would have they reproduced? Why is it that large animals these days barely have offspring with visible mutations, whereas at some point this should have been at least somewhat more common?

A few things. First, in almost all cases, the differences in appearance between parents and offspring are not the result of new mutations, they are the result of novel combinations of genetic material from each of the parents. A new mutation is exceedingly unlikely to make a particularly noticeable difference in appearance unless it "breaks" something and you wind up with a genetic disease.

 

Second, you are drastically underestimating how long evolution takes. Outside of some very extreme selection pressures, you're not going to see a difference in the population from one generation to the next. Evolution occurs faster the more frequently you reproduce, but for anything large that reproduces at a rate measurable in years or decades, evolution isn't going to take place in a span of years, decades or even centuries. It will take hundreds of thousands to millions of years for enough changes to accumulate for really significant changes to a phenotype to become apparent.

 

Evolution hasn't slowed down; it has always been a very slow process. It's more readily observable in small things that reproduce quickly like bacteria which can go through hundreds of generations very quickly. That's what causes a lot of our antibiotics to become ineffective. The ones that are most susceptible are killed off by the medicine leaving only resistant strains that the medicine can no longer combat.

 

Third, on that subject, the initial life on Earth would not have been a bacterium. Bacteria, while single-called, are actually fairly complex organisms and the result of billions of years of evolution. The initial life form(s) would have been much simpler.

 

You seem to have some misconceptions about how evolution works, which is fine. It took a couple years of reading about it in my spare time before it really clicked for me. Some of that is simply down to the fact that everything you see on TV or movies, pretty much everything you can absorb through cultural osmosis about evolution other than "there is something called evolution that happens" in fact, is completely wrong.

 

Before I dive into that, can I ask how much you know about how genetics works? Understanding evolution, at least the basics, doesn't require a particularly in-depth understanding of genetics but knowledge at least on the level of what a Punnett square is and how dominant and recessive traits work is exceedingly helpful.

[MirceaKitsune]

I might indeed overestimate the speed of evolution then. My idea was that in the beginning, simple creatures had a lot of major mutations upon birth, where some 1 out of 1000 helped with survival. Considering that some small creatures even reproduce once an year, it caused the impression that life evolved very fast at first, but the process has now slowed down as creatures got bigger.

 

I'm not very experienced with biology and physics otherwise, at least yet. It's mostly this year that I started getting into science and learning about things. Obviously this isn't enough time to learn all of the details, but I'll hopefully get a better understanding in time.

[Endy0816]

This would be more applicable to some of the earliest life. Was a long time from that point to multicellular lifeforms.

 

Generally you see a trend to minimize the impact of random mutations and to promote adaptation via safer means(recombination, multicellularity, horizontal gene transfer, etc).

Edited August 4, 2014 by Endy0816

[Delta1212]

This would be more applicable to some of the earliest life. Was a long time from that point to multicellular lifeforms.

 

Generally you see a trend to minimize the impact of random mutations and to promote adaptation via safer means(recombination, multicellularity, horizontal gene transfer, etc).

Life has long since evolved to be better at evolving, basically.