BBC Knowledge 2017 02

QUESTIONS

AND ANSWERS

14 February 2017

How fast could you

cycle in a vacuum?

When you ride a bike normally, the wind

resistance increases with the cube of

your speed. At 32km/h, the power

needed to overcome the drag accounts

for more than 75 per cent of the total

cycling effort, and this rises to over

80 per cent at 40km/h. Recumbent

bikes, which have much lower profiles

to reduce their wind resistance, can

already reach speeds of over 80km/h.

If you removed air drag completely,

the only friction would be from the tyres

and the bearings. Provided you had

a high enough gear ratio to allow your

legs to pedal at an efficient pace,

you could probably reach well over

150km/h. An easy way to simulate

this would be to try pedalling on a

stationary bike, but there are no

published records for this sport. LV

Are humans naturally

monogamous?

Humans aren’t sexually monogamous in the sense that many

birds are. Geese form lifelong couples and virtually never mate

with anyone except their partner. We are termed ‘socially

monogamous’ by biologists, which means that we usually live

as couples, but the relationships aren’t permanent and some

sex occurs outside the relationship.

There are three main explanations for why social monogamy

evolved in humans, and biologists are still arguing, which is the

most important. It may be because human babies need a lot of

looking after and stable couples can share the parenting burden.

Or it could be because men want to stay close to prevent their partners

from cheating. And it could also be a strategy that women evolved to

discourage men from killing infants that they suspected were not theirs.

Monogamy in humans is beneficial because it increases the chances of raising

offspring, but it is actually very rare in mammals – less than 10 per cent of mammal

species are monogamous, compared with 90 per cent of bird species. Even in

primates, where it is more common, only about a quarter of species are monogamous.

Our early ape ancestors weren’t monogamous and the practice probably didn’t take

off until Homo erectus emerged, around 1.9 million years ago. LV

VITAL STATS

The amount of egg cells

present in a 20-week-old female foetus,

decreasing to about

a million at birth.

7 million

GETTY X7, ISTOCK

14 February 2017