Comments on: In the footsteps of my lactose-intolerant ancestors http://blogs.discovermagazine.com/loom/2007/02/26/in-the-footsteps-of-my-lactose-intolerant-ancestors/ A blog about life, past and future. Written by DISCOVER contributing editor and columnist Carl Zimmer. Mon, 13 Feb 2012 19:00:24 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: fnxtr http://blogs.discovermagazine.com/loom/2007/02/26/in-the-footsteps-of-my-lactose-intolerant-ancestors/comment-page-1/#comment-4487 fnxtr Wed, 28 Mar 2007 16:33:30 +0000 http://blogs.discovermagazine.com/loom/2007/02/26/in-the-footsteps-of-my-lactose-intolerant-ancestors/#comment-4487 Sean: Could your observation be partly because the population isn't as culturally homogenous as it was when we were growing up? Just a thought. Sean:
Could your observation be partly because the population isn’t as culturally homogenous as it was when we were growing up? Just a thought.

]]> By: P. Jennings http://blogs.discovermagazine.com/loom/2007/02/26/in-the-footsteps-of-my-lactose-intolerant-ancestors/comment-page-1/#comment-4486 P. Jennings Mon, 26 Mar 2007 00:13:04 +0000 http://blogs.discovermagazine.com/loom/2007/02/26/in-the-footsteps-of-my-lactose-intolerant-ancestors/#comment-4486 The problem with digesting milk is not just related to lactose. If it were, then the very many people who have tried taking lactase along with milk -- or who have tried drinking milk with 'lactase added' -- would have no problem. They do have a problem. Digesting the milk still doesn't work. There are many ingredients in milk, and each one can pose its own difficulty. The idea that it's just a 'lactose' problem is far too simplistic. The problem with digesting milk is not just related to lactose. If it were, then the very many people who have tried taking lactase along with milk — or who have tried drinking milk with ‘lactase added’ — would have no problem.

They do have a problem. Digesting the milk still doesn’t work.

There are many ingredients in milk, and each one can pose its own difficulty.

The idea that it’s just a ‘lactose’ problem is far too simplistic.

]]> By: Sean http://blogs.discovermagazine.com/loom/2007/02/26/in-the-footsteps-of-my-lactose-intolerant-ancestors/comment-page-1/#comment-4485 Sean Tue, 27 Feb 2007 17:40:22 +0000 http://blogs.discovermagazine.com/loom/2007/02/26/in-the-footsteps-of-my-lactose-intolerant-ancestors/#comment-4485 As a person who does have an issue with the consuming of lactose products i do believe that more people are developing the inability to process lactose. I was able to consume lactose till i was around 15 years old, up until that point i would drink on average 2 liters of milk per day. I am the only person within my family that is unable to consume lactose, and this does include all my living relatives. Mutant dna may be to blame for this. So I'm not sure if the passing down of lactose-associated DNA to their descendants is true, I'm sure it plays some part within the ability to process lactose but I'm also sure that hormones and other things that are added to milk also play a part of the lactose intolerance. I've noticed that alot more children are lactose intolerant, when i was growing up i knew of one child within my junior years that was lactose intolerant and he grew out of this. I'd love to be able to process lactose without the aid of a pill, even when i do i notice that there are still some issues that are associated with lactose intolerance. As a person who does have an issue with the consuming of lactose products i do believe that more people are developing the inability to process lactose.

I was able to consume lactose till i was around 15 years old, up until that point i would drink on average 2 liters of milk per day.

I am the only person within my family that is unable to consume lactose, and this does include all my living relatives. Mutant dna may be to blame for this.

So I’m not sure if the passing down of lactose-associated DNA to their descendants is true, I’m sure it plays some part within the ability to process lactose but I’m also sure that hormones and other things that are added to milk also play a part of the lactose intolerance.

I’ve noticed that alot more children are lactose intolerant, when i was growing up i knew of one child within my junior years that was lactose intolerant and he grew out of this.

I’d love to be able to process lactose without the aid of a pill, even when i do i notice that there are still some issues that are associated with lactose intolerance.

]]> By: jackd http://blogs.discovermagazine.com/loom/2007/02/26/in-the-footsteps-of-my-lactose-intolerant-ancestors/comment-page-1/#comment-4484 jackd Tue, 27 Feb 2007 16:31:47 +0000 http://blogs.discovermagazine.com/loom/2007/02/26/in-the-footsteps-of-my-lactose-intolerant-ancestors/#comment-4484 Roy - you're assuming basically zero cost for generating lactase, which is almost certainly wrong since Carl points out that lactase production shuts down in all mammals. So the question becomes whether the benefit of being able to digest that milk offsets the cost. If it were net advantageous, I'd expect at least some predators would have evolved the trait. Roy – you’re assuming basically zero cost for generating lactase, which is almost certainly wrong since Carl points out that lactase production shuts down in all mammals. So the question becomes whether the benefit of being able to digest that milk offsets the cost. If it were net advantageous, I’d expect at least some predators would have evolved the trait.

]]> By: BC http://blogs.discovermagazine.com/loom/2007/02/26/in-the-footsteps-of-my-lactose-intolerant-ancestors/comment-page-1/#comment-4483 BC Tue, 27 Feb 2007 02:56:26 +0000 http://blogs.discovermagazine.com/loom/2007/02/26/in-the-footsteps-of-my-lactose-intolerant-ancestors/#comment-4483 Here's a link to a similar story - this one looked at the alleles in the African Kenyan/Tanzanian population. <i>Sequencing and gene expression analysis revealed that these people carried a single mutation that allowed high levels of adult lactase expression, but that the mutation was different from the one present in Europeans. They also found that this new mutation had undergone a powerful selective sweep through the population. Those without the new allele typically had identical DNA sequences for about 1.8 kilobases around the gene. In those with it, the identical region stretched to over two Megabases - a difference of three orders of magnitude. Clearly, this allele has spread recently and rapidly, and has been under intense selective pressure.</i> <i>The authors estimate the age of the allele as recently as 2,800 years ago, which is in good agreement with estimates of the arrival of cattle into the Tanzania area about 3,300 years ago. But they also note that cattle spread through Africa over a period of thousands of years, and that other ethnic groups from the continents appear to be able to digest lactose, but don't share the Kenyan/Tanzanian or European allele. Thus, it appears that there may be other mutations left to discover. </i> <a href="http://arstechnica.com/journals/science.ars/2006/12/11/6246" rel="nofollow">http://arstechnica.com/journals/science.ars/2006/12/11/6246</a> Here’s a link to a similar story – this one looked at the alleles in the African Kenyan/Tanzanian population.

Sequencing and gene expression analysis revealed that these people carried a single mutation that allowed high levels of adult lactase expression, but that the mutation was different from the one present in Europeans. They also found that this new mutation had undergone a powerful selective sweep through the population. Those without the new allele typically had identical DNA sequences for about 1.8 kilobases around the gene. In those with it, the identical region stretched to over two Megabases – a difference of three orders of magnitude. Clearly, this allele has spread recently and rapidly, and has been under intense selective pressure.

The authors estimate the age of the allele as recently as 2,800 years ago, which is in good agreement with estimates of the arrival of cattle into the Tanzania area about 3,300 years ago. But they also note that cattle spread through Africa over a period of thousands of years, and that other ethnic groups from the continents appear to be able to digest lactose, but don’t share the Kenyan/Tanzanian or European allele. Thus, it appears that there may be other mutations left to discover.
http://arstechnica.com/journals/science.ars/2006/12/11/6246

]]> By: Roy http://blogs.discovermagazine.com/loom/2007/02/26/in-the-footsteps-of-my-lactose-intolerant-ancestors/comment-page-1/#comment-4482 Roy Mon, 26 Feb 2007 23:30:23 +0000 http://blogs.discovermagazine.com/loom/2007/02/26/in-the-footsteps-of-my-lactose-intolerant-ancestors/#comment-4482 Actually, there is a use for lactase in adults, if the adults of that species prey upon mammals. On killing a lactating mammal, no predator in its right mind would miss the chance to consume all of the available milk. Actually, there is a use for lactase in adults, if the adults of that species prey upon mammals. On killing a lactating mammal, no predator in its right mind would miss the chance to consume all of the available milk.

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