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usafjay1976

Oldest Ever Human Dna Found In Spain - New Questions About Evolution

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So I found this article the other day and wanted to get your inputs.

 

http://www.theverge.com/2013/12/4/5175488/researchers-find-400000-year-old-human-dna-spain-oldest-found

 

Seems like they found DNA from a femur that is 400,000 years old.

 

I like one of the quotes in the article from Juan Luis Arsuaga. He says, and I quote,

 

 

Now we have to rethink the whole story

 

Ah yes, let's see how we can make it all fit so it makes sense!

 

Question for anyone here, how is DNA tested to determine the age? How long does DNA last before it decays?

 

Here is another article with a few pictures of the bones.

 

http://www.bbc.co.uk/news/science-environment-25193442

 

Anyone good with bones? (Bonedigger?) smile.png

 

 

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>First, following from Fjuri, the popular article you are reading is a rehash by some random news blogger who plausibly doesn't have much more insight into DNA or early humans than most people, so beware of massive inaccuracies - same for any news report.

 

On the "Now we have to rethink the whole story" -> 'Ah yes, let's see how we can make it all fit so it makes sense!'

 

> Yes indeed. That's what science does, that's the power of it. New discoveries that appear reliable (i.e. well evaluated with rigourous modern methods) much be fitted into the scheme, which in cases like this require the current view of grand scheme of hominids in Europe to be altered. It's wrong to say 'the whole story' because what story ? I'd expect 'hominids in Europe story' not 'how all life originated story, etc'

 

So, "Question for anyone here, how is DNA tested to determine the age? How long does DNA last before it decays?"

 

> Part A: The age is partly determined from the other standard fossil dating methods, mainly radiometric dating, but also looking at other fossil clues in the same soil levels, looking at pottery or tool clues in the same soil levels etc. BUT, also the DNA itself can generate independent dating estimates, basically by running DNA comparisons in computer software that looks at number and placement of changes amongst sites (bases) and using complex models of how DNA changes (substitutions) accumulate over time, makes an estimate of how amount of infered divergence can relate to a time scale - given e.g. we've observed in the lab that that the same piece of DNA will show X number of Y type of changes over e.g. 20 years laboratory tracking accumulated differences.

 

>Part B: No clear answer is possible, it depends on huge number of factors, but basically, in the absence of free water any DNA degrades quickly, but when water is limited by desiccation or freezing, the decay process slows dramatically. Type of tissue also really matters, DNA in outer soft tissue degrades rapidly, within the core of bones much more slowly. So, all depends on tissue and conditions, but also very difficult to answer when you generalise to just 'DNA', as are we talking whole genomes, whole chromosomes, part chromosomes, actively transcribed genes, mitochondrial genomes etc. Basically whole genomes degrade into pieces quickly, some copies faster than others, but if your just after small pieces of non-transcribed regions, those are much more robust (protected by binding proteins, and smaller pieced last longer against degradation than longer pieces). These days however genetic technology is getting dramatically better, so we're becoming able to salvage information from very few surviving copies of ever bigger pieces from increasingly poorer preserved tissue, whereas before, it was only very small fragments from very well preserved sources. Times are changing, ever more evidence is becoming available from ever older fossils.

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