woman: X-chromosome, another redundant X-chromosome.
The "98% similarity between Human and Chimp DNA" is concentrated on the X-chromosome.
The Y-Chromosome on the other hand is more than 30% different between Humans and Chimps and evolving.
Thus it seems that X-chromosomes make us more similar to unevolved animals and Y-chromosomes makes us more similar to the Sentient Human beings we are.
Even in Evolutionary Psychology, if we extrapolate these findings, we notice that of the two genders, the one which behaves more "emotionally, impulsively and irrationally" (in short like non-sentient animals) is the female human gender with double the X-chromosomes.
And of course the gender that behaves more rationally, logically and is responsible for 99.9% of ALL Human Achievement if not more is the only one with a Y-chromosome in addition to an X, i.e. Men.
Men are, in short, the drivers of evolution, while women are a backup foundation of our biological makeup. Backup foundations because Men already possess an X-chromosome foundation built in.
The Y-chromosome is responsible for evolution, adaptation, survival and reproduction to an extremely Huge degree. While the X-chromosome is like a foundation for the Y to work on.
Thus, while an X and a Y combination have sufficient genetic material to replicate an XX or XY combination, the same, sadly cannot be said for the XX combination.
Two foundations don't make a monument, but a foundation and scaffold do. Human Civilization is testament to this truth.