In the majority of cases, life is more risky for the males, because they either succeed
or fail, whereas almost all the females breed. That is why evolution has made the males bigger
and more aggressive. It is the female who must choose the best genes, because her eggs
are few, limited and valuable, and what’s more it is they who will have to look after
the young. For a male, the cost of an error is insignificant, his sperm can easily be
replaced. In humans, for example, a woman produces just 400 eggs in her entire life,
but a man releases 300 million sperm in each ejaculation.
The Magellanic penguin is colonial and monogamous, so while some males are with their lifelong
mate, others, still single, try to find a partner. But it is not easy.
While others triumph, he is scorned.
Despite the insistence of this male, the female rejects him because he does not have his own
hole in which to lay the eggs. No way is she going to risk reproducing with someone who
is not even capable of getting there in time to grab a decent home.
And without a home sweet home, the girl simply isn’t interested, no matter how much he
insists.
For the female, it is very important that the future father of her eggs has his own
living quarters. So if this male wants a mate he’ll just have to get here a bit earlier
next year.
Almost all animals have one breeding season a year, but there are two species for which
this is not true: rats and humans. Human females are always sexually active, and childhood
is long, so the couple needs to be a stable unit. And that is of enormous biological importance
because it is vital for the survival of the young.
This is Papua New Guinea, and in the Highlands a marriage is taking place. The bride shows
off the money the groom has paid, in addition to thirty pigs. The bride and groom are from
different villages, and now the two families are gathered together, the bride price can
be handed over.
In all human cultures, the union of the couple also involves the families and the clans.
Without the support of their social groups, a new family would get off to a very bad start.
Once the deal has been made, the bride’s family takes their share of the food and goes
to their village.
The longevity of humans means there can be prolonged contact between generations, favouring
a lasting biosocial and mental evolution.
After the formation, however temporary, of the couple, and as a result of this, reproduction
brings the birth of new individuals.
For the majority of mammals, the adaptive success of the males is based on breeding
with many females, then giving little or no help in raising the young. So, the females
are often left to look after the children alone.
This female bear has to teach her two cubs how to fish for salmon, but at the same time
must avoid any encounter with a male, who would not hesitate to kill her cubs so she
will again come into heat.
The cubs would not be able to survive in the future without the lessons they learn from
their mother during the first three years of life. During this time, even their own
fathers would not recognise them, and would kill them. The maternal bond is without doubt
the strongest in nature, any mammalian mother would give her life to save her children,
and would be capable of facing any danger for them, she is a super-animal, ready to
sacrifice all.
But if she died, the young would not last long, so evolution is on the side of mothers
who know when to beat a hasty retreat.
A male is fishing rather too close, so it’s best to leave.
The elephant seals are not exactly model fathers either. In their obsession with defending
their harem, these colossi push, oppress and even crush the young who, as the almighty
sultan rushes past, are often separated from their mother and get lost. They are the pups
born the previous year, and they will continue to breastfeed for four more weeks, breastfeeding,
before their mothers go into heat and are again mounted by the stud male.
Up to ten per cent of cubs are killed, crushed by their father.