But we’re only just now beginning to understand the full advantage that this extra X chromosome confers: It’s not just that women have a spare X chromosome to swap in. Rather, the more than 2,000 genes that, combined, make up two X chromosomes, are used by cells that actually interact and cooperate within a woman’s body. Each cell predominantly uses one X chromosome over the other — so if one X chromosome has genes that are better at recognizing invading viruses like Covid-19, for instance, immune cells using that X can focus on that task, while immune cells using the other X chromosome focus on, say, killing cells infected with Covid-19 instead, making the fight against the virus more efficient.
Typical males, by contrast, are forced to get by in life with just the one X chromosome. What if a male’s particular genes aren’t able to competently recognize or kill off cells infected with a coronavirus? In that case, his ability to fight the infection will be limited; his solitary X is the only one he’s got.
The bottom line is when it comes to dealing with the trauma and stressors of life — whether it’s avoiding a serious congenital malformation, a developmental disability, or fighting off an infection — females have genetic options. And genetic males don’t.