Tuesday, 10 January 2012

#15 Pity the hyena mother

FACT OF THE DAY: It turns out that our bodies are not the only ones that are badly designed for childbirth. Hyenas give birth through their CLITORIS!

In a previous post I wrote about us humans being relatively badly designed for childbirth compared to the other great apes. (Post #3 http://pregnancyandchildbirtharoundtheworld.blogspot.com/2011/10/childbirth-are-our-bodies-designed-for.html).  Because of our large brain size our babies have big heads, and because we walk upright our pelvis has a small hole – the combination of these two factors can be lethal for mother and baby.

When you think about it, this is a pretty major design fault. No doubt some population geneticist could explain the costs and benefits to me, but from a species point of view (never mind the individual woman’s point of view) it seems odd to kill off one generation in producing the next.

Anyway, at that point I kind of thought that humans were unique in risking death and injury each time they gave birth. Clearly the other great apes did not suffer from this, and I had never really heard of other female species dying giving birth to their young. Based on absolutely no knowledge I had a vague feeling that because most other mammals give birth to such tiny babies relative to their body size, the babies just sort of slip out.

However, there is at least one mammal that breaks the rule.

Take for example the hyena.

Firstly, the female hyena’s birth canal is V-shaped AND twice the usual length for a mammal her size, so that the baby has to travel quite a distance and make a 180 degree turn on its journey into the outside world.   Secondly, she has no vagina and the birth canal leads into the clitoris, which sticks out 7 inches, rather like a penis. As the baby is squeezed out through this long clitoris tube, the clitoris itself is stretched and often tears.

(Amazingly this one exit hole through her penis-like-clitoris is also where the hyena mother wees out of, and how she has sex. I can’t quite imagine how that would work. One theory is that as this makes sex so difficult without the full cooperation of the female, it effectively means that forced sex is not an option in this female dominated society).

Many first time hyena mothers die giving birth, and 60% of infants being born to first time mothers suffocate and die passing through ‘the eye of this needle’.

Suddenly our experience of childbirth doesn’t seem so bad...

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If you would like to read more yourself, take a look at;

Blaffer Hrdy, S (1999) Mother Nature; A History of Mothers, Infants and Natural Selection United States of America : Pantheon Books

S. M. Dloniak, J. A. French and K. E. Holekamp (2006) Rank-related maternal effects of androgens on behaviour in wild spotted hyaenas Nature 440, 1190-1193 (27 April 2006) doi:10.1038/nature04540

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