Science Sunday: Female? Old? Thank Your Mitochondria!
So for those of you who don’t know, females in general live longer than males. This isn’t just a human phenomena either, in fact, the scientist’s best friend, the fruit fly, has helped us get a step closer to resolving the mystery I like to call: ‘Rise Of The Old Women’. As it turns out, the answer is rather interesting; join me after the jump.
The source of this difference seems to lie in the mitochondria; our cells’ energy factories. These organelles have their own DNA; a relic from their bacterial origins (before they got all cosy inside other cells and became BFFs with our bodies, it’s largely thanks to them that we have enough energy to support the energy intensive processes we go through as multicellular organisms), DNA that passes through the generations down the female line, each child receiving their mitochondria from their mother.
Do you see where this is going?
As much as we might automatically assume that because it’s women that are living longer they’re the ones receiving an effect, it’s actually the other way around. According to Dr. Damian Dowling from Monash University ‘there are numerous mutations in the mitochondrial DNA that effect how long males live and the speed at which they age’; and despite assumptions we might make about males and aging due to the George Clooneys that only ripen with age, these dampening effects actually have no effect on females.
So what does this mean?
Because only females pass on mitochondrial DNA, evolutionary forces are generally more successful if they favor the ability of females to pass on their genes as much as possible into the next generation. However, because no males pass on mitochondria, mitonchondrial DNA can cause otherwise unfavorable effects in males and still get successfully passed on through generations, because the DNA causing the detriments is having no effect on the females that pass on the DNA.
Of course the rules of natural selection still apply; if there was a crippling detriment in the mitochondrial DNA, less men with that DNA would reproduce and evolution may cast a dark hand; however, with subtler changes like life expectancy and aging, these effects can proliferate while leaving the population pretty much unscathed; and given the age gap’s proliferation in the animal kingdom this seems like it might just be the case.
By examining mitochondrial DNA in fruit flies, scientists were able to observe a number of these DNA regions; it would seem that they’re more than prevalent in our genetic makeup, so, to all of you skepchicks, thank your mitochondria for what could be a long life ahead, and for my fellow skepdudes… I’ll be preparing my sub-cellular army to march on my mitonchondria soon. Meet my troops inside my cells and we will make our terms with the usurpers.
[source: BBC: http://www.bbc.co.uk/news/health-19093442, image credits: themagicschoolbus.blogspot.com, apartmenttherapy.com]