If I remember correctly you studied math, didn't you? Competition for a job in math is way lower than it is for biological sciences. The reason is that the current model of a successful biology lab is that of a PI leading a number of students and postdocs anywhere from 5 to 20. There is NO WAY that all of them are going to find a job in academia. Germany alone produces in one year the same number of PhDs as there are professors in the country. Ratios are not very different in UK and US. Most of the competition happens in the biological sciences: you can run math or CS research by yourself. Difficult to do the same in biology.
"Competition for a job in math is way lower than it is for biological sciences."
Actually, the opposite is true, at least in the United States. Many more Biological Science PhDs are granted relative to mathematics, but there is also a lot more funding in the life sciences relative to mathematics.
The mathematics job market is more similar to the notorious humanities market than to the life sciences.
You hardly have postdoctoral positions in math, physics and social sciences. Lots of people still manage to get an assistant professor position after PhD. Postdocs emerged only recently and they are a buffer for those who cannot get a TT job after PhD. In biology it is absolutely normaly, in fact necessary, to go through ~5 yrs of postdoc before dreaming of applying. The estimates I know about math is that 1/5 of graduated get a job in academia. In biology is about order of magnitude more difficult (some less backed up estimates even claim is 1/300).
"You hardly have postdoctoral positions in math, physics and social sciences."
I don't know anything about the social sciences. In physics, I know that postdocs are absolutely necessary and expected, to the same degree that they are in the life sciences.
Mathematics is a little different. There are a very small minority of prodigy-types that go right from graduate school to the tenure track. However, post-doc's are still the norm, although they don't go by the name 'postdoc.' Usually they are pronounced 'visiting assistant professor' or 'instructor.'
Here's an example of a 'postdoc' in mathematics. All of the big universities have them:
I've written about it here: http://gilest.ro/2010/what-has-changed-in-science-and-what-m...