Showing posts with label Humans. Show all posts
Showing posts with label Humans. Show all posts

Take Care Of Your Ys Guys


A very long time ago, about 200 million years, our ancestor’s chromosomes had developed the X and Y types that stand us in good stead today. We share a lot of our DNA with other primate species as the species diverged about 25 million years ago.

Us males are very dependent on our Y-chromosomes; especially the male specific part and over the years there has been a lot of fraying around the edges so that we only have about 3% of the original version from 200 million years ago. We have known about this for some time and there has been some concern that men may be getting perilously close to their “sell by date.”

The X and Ys started out with about the same number of genes. Currently the X has around 800 while the Y is down to its last 78. This represents about 3% of what it started out with, hence the tendency for us to start biting our fingernails.

To put our minds at rest (or worry us some more) Hughes et al have sequenced the macaque genome to see if they have suffered a similar loss (1,2). These monkey’s ancestors diverged from ours about 25 million years ago as noted above.

The good news is that since the great divergence from the monkeys, we’ve only lost one gene to bring us down from 79 and we’ve been keeping a firm grip on those 78 for the past 5 million years so our male specific part of our Y-chromosome is in good hands.

Recall that the chimpanzees went off on their own about six million years ago and it was in Hughes et al’s letter to Nature (3) comparing the chimpanzees Ys with ours that started us worrying back in 2005.

  1. http://www.nature.com/nature/journal/vaop/ncurrent/full/nature10843.html
  2. http://www.bbc.co.uk/news/science-environment-17127617
  3. http://www.nature.com/nature/journal/v437/n7055/full/nature04101.html


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Too Late!


Our experiences in the first few years of our lives have enduring effects on the way we behave later. At that early age we have little or no control on what is going on. Of course, now that we’re grown up, we don’t recall much of those early days and would probably assume that it is our later experiences that mostly shape our behavior. But this may not be so.

 A study by Feng et al from the Kunming Institute of Zoology report this week on a study of rhesus monkeys in which some youngsters who were separated from their mothers at birth, who were hand reared for the first month and then were reared with another youngster (1). The maternal separation was due to problems such as inexperienced moms not handling their babies properly, bad weather that is hazardous for young baby monkeys etc. and not for the purpose of studying the effects of the separation.

These peer-reared monkeys behave differently from those normally reared by their moms even three years later. They spent a lot of their time sitting around on their own and were generally less rhesus monkey-like.

When the monkeys were caught for check-ups, the control group, that is monkeys reared by their moms in the normal manner, responded with the release of cortisol. Cortisol, you’ll recall, helps us to get out there and fight for our survival. The guys who had been raised without their moms, had a much slower, and hence lower, cortisol release, so in a bad situation, they would be more likely to lose.

This effect of early life bad times is also seen in people. Published this week is a meta-data study of problems of depression in later life of children who had been maltreated and the depression treatments had poor outcomes. This work was carried out by Nanni et al from London’s King’s College (2).

Seriously scary to see how long term, permanent even, some of these effects can be on brain functionality.

  1. http://www.pnas.org/content/early/2011/08/12/1010943108.full.pdf+html
  2. http://ajp.psychiatryonline.org/cgi/content/abstract/appi.ajp.2011.11020335

Getting Small-minded


As we get older we look wrinkly on the outside, although we feel pretty much the same inside, but at some point, we start to suffer from a lack of velocity. As we gradually improve medical methodologies, our life expectancy increases, if and only if, we can still move fast enough to cross the road before the faster and faster cars catch us.

A question we could ask, but never do, of course, is how old are we supposed to get? If you are a cat or a dog 15 to 20 is pretty much all you can expect. If a macaw, maybe 70, but if a giant tortoise you could be looking at 150 to 200 years of silly politics. So where do we fit in?

Back to our closest animal relative, the chimpanzee, 50 years old is about it, and they don’t have to put up with the stress of studying stock market fluctuations. Sherwood et al in the current issue of the Proceedings of the National Academy have attacked this question of comparisons by using MRI scans of chimpanzee and our brains (1).

Looking at almost a hundred chimpanzees of a range of age from young to old, they found that their brain volumes were pretty constant. Well perhaps that’s a slight overstatement if one looks at the data, but there wasn’t a trend for loss of their little grey cells with age.

Not so with us humans though. With almost as many humans from 22 to 88, the brain scan showed that we were losing cells on the way to become small-minded with age. The authors point out that we are unusual in this rather careless habit (and another recent paper has shown that its not due to the demon drink) as other species don’t appear to do this and have their hippocampus and frontal lobes shrink.

Interestingly, their conclusion is that, maybe, we have reached our sell by date when our brain starts to shrink. Evolutionwise, we should have popped off by then and our extended lifespan is to blame. Philosophically, this seems to me to be a very scary thought to follow down its rabbit hole. Should monitoring changes in our brain volume become as routine as measuring our changes in cholesterol or blood glucose? Would that information be useful to health insurance providers?

  1. http://www.pnas.org/content/108/32/13029