From a population of about 1300 individuals, it took 900,000 years to grow to todays 8 billion, theoretically.

https://www.smithsonianmag.com/science-nature/genetics-suggest-our-human-ancestors-very-nearly-went-extinct-900000-years-ago-180982830/

https://archive.org/details/TimeLifeVideoWhereDidtheColoradoGo

Where Did the Colorado Go?

by WGBH (Television station : Boston, Mass.), British Broadcasting Corporation., Time-Life Films.

Publication date 1976 Topics nova (television program), Stream conservation, Colorado River (Colo.-Mexico), North America – Colorado River Publisher [New York] : Time-Life Films Language English Item Size 1.4G

Considers the destructive effects of damming and regulation of the Colorado River. Examines the problems resulting from man’s alteration of nature and discusses alternative solutions offered by conservationists.