Science Questions

Is there a scientific way to measure human age which is equivalent to tree rings? Felix

Chris -  I was thinking about this because we talked on the Naked Scientists a little while back about how researchers in Scandinavia have worked out how long a fat cell survives inside a human body by using carbon dating.  He’s saying carbon dating can be used for rocks and things like tree rings to work out how old trees are, what about humans?  The thing is when you take into your body some plant matter it’s go carbon-14 from the environment.  That gets incorporated into your body and therefore it gets written into your DNA if you have new cells being born.

What these researchers, Kirsty Spalding and her colleagues, did (they published this in Nature a couple of months ago) what they did was to take fat cells and look at how much carbon-14 they had in them.  As your fat cells age they’ll lose their carbon-14.  The amount of carbon-14 gives you an idea as to how recently that cell was born.  It will have had new DNA put into it which would have had a fresh level of carbon-14 in it when it was born.  They did actually show that fat cells have a lifespan of about ten years.

Kat -  There’s another way of doing it which is to look at your telomeres.  Inside all our cells we have chromosomes.  These are long lengths of DNA.  At the end of them, in the same way that you have a little plastic cap on the end of shoelaces you have these structures called telomeres.  These get shorter and shorter as we go through life.  Every time a cell divides it loses a bit off the end of its telomeres.  There may be some way of measuring human lifespan in terms of how long or how short your telomeres are.  The trouble is that there’s no standard length and people have different length telomeres depending on their genetic makeup.  I know that Cancer Research UK is funding a project looking at how our genes determine our telomere lengths.  It’s actually linked to cancer risk.  People who have very short telomeres are going to get shorter very quickly and that can actually increase the likelihood of getting cancer.

Chris -  So we could look at the cells, see what the length of the telomeres are and that would give you some idea as to the age of that cell?

Kat -  It would give you some indication and maybe if you compared it to other cells in the body like maybe your germ cells that don’t go through this kind of process.

July 2008