Absolutely. The overwhelming majority of humans are heterosexual and only a tiny percentage of humans are gay or even bisexual. Heterosexuality is simply the default among humans.
Good data from Australian medical students from one of the world’s top sexologists found that at the time of the survey in the 1980’s, 94% of men and women are maximally attracted to the opposite sex. 93% of men and women are straight or lean straight.
Only 6% of men and women are gay or lean gay, and in fact, many recent studies show that that figure may even be high.
Repeated surveys in the US show that ~3% of men are gay and 2% are bisexual, and ~1.5% of women are lesbians and another 1.5% are bisexual. These figures have been flat for several years now.
More recent studies of young women in the West have shown a high rate of bisexuality among young women aged 18–30 in recent years, an average of 12%. This indicates a dramatic increase in female bisexuality in recent years. It is not known what caused the increase, but I doubt if it was organic. Not all bisexual women are “born that way.”
Personally I think that despite the surveys, up to ~6% of men may be either gay or lean gay. Only 4% should really be classed as gay, and the rest would be gay-leaning bisexuals. This is close to the 5% gay or bisexual figure found in the survey discussed in the second paragraph.
Probably ~1–2% of women are lesbians. Rates of female bisexuality are variable and are discussed above.
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Heterosexuality is the default human position, absolutely. Evolutionary pressure alone assures that. However, don’t forget the importance of ‘situational homosexuality’. Extreme examples of this occur in prisons, boarding schools and other single-sex environments. Although more work has been done on the male variant, it happens in women too. This means that in some cultures the number of people who have, perhaps even regularly, indulged in homosexual behaviour, is much greater than the number of those for whom it is their primary orientation. This even becomes a defined feature, in many cultures, where young males go through a phase of being submissive sexual partners to older ones. Once they get older, they adopt the dominant role BUT they also marry women and become fathers.
Homosexuality is a very complex phenomenon, massively influenced by culture. I think this is because the imperative to have sex, particularly for men, is stronger than the imperative for heterosexual sex.