Page 91 - How It Works - Book Of Amazing Answers To Curious Questions, Volume 05-15

Science

Why do some people have

wisdom teeth?

f you trace human evolution right back Today, we no longer need our wisdom
I to our early ape-like ancestors, you’ll teeth, and for many people they are a

find that they had much larger heads and problem. Our jaws are small, and wisdom
jaws than we do now. Their teeth would teeth don’t always have space to come
have been used for biting, crushing and through straight. They often need to be
grinding food well before we had removed because they are causing pain,
developed the means to chop and cook it. or damaging the surrounding teeth.
As we evolved and our diets changed, our Around 35 per cent of the population do
teeth were no longer our primary tool, and not have any wisdom teeth at all, and there
as our brains grew larger, our jaws is some debate as to whether they will Why are some
became shorter. eventually disappear all together.
people left-
handed?

round ten per cent of the general
Apopulation is left handed, and
How do according to archaeological evidence, this
proportion has remained the same for
we become around 5,000 years. A mathematical model
developed by Northwestern University has a
resistant possible explanation.
Humans are a competitive species, and
to antibiotics? historically we fought hand-to-hand to settle
disputes. In direct competition, left-handers
have the advantage because their stance is
t’s not us that become resistant, unusual, and in one-on-one sports like
I it’s the bacteria we are trying to fencing and baseball, there are many more
kill. Bacteria multiply quicker than left-handed athletes than you might expect.
other organisms and have simpler If this were the only affecting factor, the
genomes, so random mutations numbers of left and right-handed people
happen more often. Some of those would eventually even out. However, even
might give them a tougher cell wall more important to humans than competition
or a way to metabolise a toxin. Low is co-operation. As a social species, one of

doses of antibiotics given to farm our defining characteristics resides in the
animals, and as medicine to humans use of tools.
who don’t really need it, provide an Left-handed people are at a disadvantage
environment that only kills the when using tools designed for right-handed
weaker bacteria. The ones that are people, and in golf, a sport where there is no
left are those with the genes for direct competition and a heavy reliance of
antibiotic resistance, so they go on specialist tools, left-handers are under-
to multiply and spread those genes. represented. This balance between the
advantage of novelty in competition and the
disadvantage of difference in co-operation is
thought to be the reason that some of the
population is left-handed.

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