30th Nov 2025

Humans, like other mammals have a male/female ratio close to 50/50. If more females were born than males, there would be the potential for much faster population growth.

To avoid population decline, and ultimately extinction, the birthrate must exceed the death rate. There may be periods of decline. There maybe periods of stability. Populations may see-saw. Species that avoid extinction will have prolonged periods where birth rates exceed the death rates.

With a 50/50 ratio, the birth rate must exceed 2 per female.

With a 100/1 ratio, the birth rate must exceed 1.01 per female.

With a 10/1 ratio, the birth rate must exceed 1.1 per female.

You can see clearly that the birthing demand on each female nearly doubles when the ratio of boy to girls being born is 50/50.

As the ratio changes, trade-offs become apparent.

The 100/1 ratio is absurd. It is unlikely to be prosperous. The single male would need to impregnate an absurdly high number of females. If he perishes the game is over for all. Getting a male from elsewhere increases the ratio to untenable levels. Extinction would be likely.

The 10/1 ratio shows more promise. A male fatality is still problematical but less troublesome. A nearby male could handle 20, or three groups of 10 could be ‘serviced’ by two males.

To have a steady state population with a 10/1 ratio and 1.1 births per female we assume all women are fertile. The male would also need to be fertile. The male must not be a retard. In practice there will be an infertility rate. There will be a retard rate too. There will also be hyper-fertile women. Some birthing twins. Some having more to account for deficiencies elsewhere in the group.

The retard may produce retarded babies. Maybe a third of his children will be useless. They will be a hinderance rather than a help when it comes to food gathering. However, set a retard a task, and the task is undertaken with little fuss or complaint. The retard will be given the task of impregnating all ten of the hareem. He will duly oblige unlike other males which show preference for having sex with certain women ignoring a lot of the others. Some of the females will do what they can to avoid becoming pregnant. Think about this before you swoon over the results that a model purports. Dodgy data. Assumptions. Biases. You name it, can swing the result.

Ratio

: 1

Fertility rate

%

Pregnancy volume

%

Infant mortality

%

Run

The difference between 5:1 ratio and 1:1 ratio is phenomenal. There is undoubtedly a lot to be said for having more females. It helps in any race. A species will flourish.

Some will contend that evolution focuses on the survival chances of the individual. The success of the species is secondary. That idea may be flawed. A species that flourishes by way of expanding quickly will expand quickly. There is no intention in evolution. Each species flourishes or fails. The ones we see today did better than the millions of others that were out manoeuvred.

If two microbes land on my cheese they will be in completion with one another for domination. The faster they spread, the more microbes they release in the air at the end to land elsewhere. The microbes will procreate unabated. From one to billions in a matter of days. It is a system that works for them. They do not think about their long-term population problems. The cheese will run out. There will be an incredible population crash when it does. One, to billions, to tens which land elsewhere to breed. The overwhelming vast majority will die.

Does this provide a clue? If mammal populations ran into the same issue, it could be calamitous for the species. From five thousand to billions in the space of a few centuries. Food could run out fast wiping the entire species of the map. Maybe this problem was encountered when we were at the fish stage of evolution. Mass population expansion followed by severe crashes. The fortuitous even sex ratio kept a lid on over rapid expansion. Males are dummies, null, population expansion inhibitors. The sex ratio balance system could be embedded deep in the core of our genes.

One thing to note is how infant mortality affects the outcome so dramatically. Infant mortality puts a significant brake on population expansion. We have seen infant mortality drop precipitously in many parts of the world. From 30 percent to around one percent in many cases. We have also seen the human population expand violently during that time. The drop in infant mortality is helping us reach a crisis point a lot quicker.

Did evolution favour males for their role in protecting? It is a nice idea. Would it not make sense to beef up the females instead. Many females can compete satisfactorily with males in regards protection duty.

Whatever theory you have, remember that the core evolution process was at a time before mammals grew and harvested their own food. We are still evolving, but very slowly. An evolutionary experiment that changes the sex ratio is borne out over many centuries.