Yes, it is complicated, I agree. I never said that biology is the only factor, it isn't.

I was using genotype/phenotype as an example of how the interplay between biology and gender might work. When I say biology, I don't mean the existence of a physical body. I mean biological systems. What is gender according to you?

If biology is acknowledged as a factor in gender expression, then the existence of transgender people makes so much more sense. Their gender expresses differently from their sex. Some people feel this difference at a young age, before they have been fully indoctrinated into all of the cultural norms of their society. Why? What is driving this?

You assert that most gender differences are due to society and culture. I'm not arguing that point. No one knows how much of gender is due to biology vs society. I guess a good place to look would be at our closest ancestors. How do chimps express gender, do they have gender roles? I will look into it, I'm curious. :)

Do you have examples of things that are purely social constructs and present in every society? I guess that's possible, but I can't think of any that can't ALSO be explained by biology. The issue that I have with the argument that "gender is a social construct" is that it is usually being presented as completely independent of biology.

I think that gender is derived from both biology and society. In genetics we have the concept of a genotype and a phenotype. The genotype is the DNA sequence and the phenotype is the expression of that DNA. I might have a DNA sequence that codes for blue eyes. The blueness of my eyes is the phenotype. I think sex and gender work the same way. My sex is female, my gender is female. There can be variations and anomalies, but female sex is generally predictive of female gender. If your sex is female, it is most likely that your gender will also be expressed as female. This doesn't negate the validity of transgender, non-binary, intersex, etc. Biology is complex. Most biological systems are not an on/off switch or a yes/no.

The reason that we don't see any example of a genderless society is because if we could remove all social rules about gender, there would still be the concept of gender, because of biology.

Much more interesting questions arise if gender is viewed as a product of both biology and society. How much of gender is due to societal influence and how much is driven by biology? What would gender be like if we could somehow strip away all gender roles and rules implemented by society? What would it feel like to be my gender under these circumstances?

If gender is a social construct, shouldn't there be examples of societies in which there are no genders at all?

A gender-less society should have zero concept of gender, humans should just be viewed as humans with no categorizing of people based on the concept of gender.

I've heard the argument that money is a social construct and this is used as an example of how gender might also be a social construct. Indeed, there are examples of societies that do not use money and have no concept of money (Awa people of the Amazon, for instance). Therefore, we should be able to identify a society that has no concept of gender.

Examples have been given of societies that acknowledge more than 2 genders, but these societies still have the concept of gender. This is simply an example of a wider view of gender, not an example of a society that has not conceived of gender.

Differences in language such as the non-existence of gender pronouns is not evidence of a gender-less society. If a society doesn't have gendered language but still acknowledges gender through societal customs, beliefs, and rituals, then this is not a true gender-less society. I could be wrong, but I don't think that such a society exists or has existed. If anyone knows of an example of a society with no concept of gender, I'd be curious to learn about it.