Bio-Tech: Altered Sex Ratio
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This (species modification) modifies the average ratio of male to female births. This can be a specific ratio (e.g., five women to every man) or even eliminate births of either sex. These changes may be made to correct a perceived imbal- ance, or for deliberate attempts at social engineering. However, although an altered sex ratio can be programmed by gengineer fiat, it will naturally drift back to equal ratios over evolutionary time, assuming the species is allowed to evolve (see below). 0 points.
Sex Ratios
Most animals we are familiar with produce equal numbers of males and females. A common method in fiction of emphasizing that a species is alien is to alter this ratio. Some thought about why real creatures have an equal sex ratio can lead to interesting conclusions about fantasy or science fiction species that don't.
It may seem evolutionarily wasteful to produce as many males as females. After all, one male can fertilize dozens of females – as is the case in harem-keeping species such as sea lions – so why use valuable food resources to produce superfluous males? The answer comes from the interplay of biology and mathematics. Let's assume:
- A species has two sexes.
- An individual inherits an equal number of genes from each parent.
- Those genes form the basis of evolution.
The evolutionary success of a group of genes is measured by one thing only: how many offspring those genes produce. If a population consists of more females than males, then – on average – each female produces fewer children than each male (since the number of children divided by the number of females is less than the same number of children divided by the number of males). So for genes to produce more offspring, it is better for them to be in a male body. Over time, evolutionary pressure will produce more males. The opposite applies if there are more males; either way evolution tends to even out the sex ratio.
For natural species in a hard science setting, assumption 3 is a given. Changing assumption 1 can lead to interesting aliens, but a similar argument proves that a species with any number of sexes must produce each sex in equal numbers.
Some familiar species on Earth don't have equal sex ratios: ants and bees. They manage this by breaking assumption 2. Male ants and bees do not have fathers – they get all their genes from their mother. The breeding members of ant and bee colonies are produced in a 3-1 female-male ratio. This also raises the question of sterile worker castes – most ants and bees are actually sterile. Since such drones don't reproduce, they don’t enter the above arguments, and can be produced in any numbers.
So naturally evolved species usually either have equal sex ratios, an unusual genetic inheritance mechanism, or sterile castes. But if they were gengineered recently (or exist in a fantasy or superscience setting), then all bets are off.