They behave as if they have "rules,laws".

The Bible explains Giants and their origins, so does ancient Greece.

Once the results in the DNA study started to become clearer, the Bible was the logical place to go for answers.

The DNA revealed Bigfoot was the result of hybridization between modern human females and an unknown male propigator. The hybridization events occurred between 12,000 and 20,000 years ago and was tracked to specific regions and specific Haplo groups traced by the female lianige. There where multiple events in multiple locations\continents roughly around the same time period which resulted in the same hybrid species distributed around the globe due to a mass hybridization event globally.

Really only the Bible makes sense, book of Enoch gets even deeper into it.