Answer:
Horizontal gene transfer
Explanation:
Horizontal gene transfer or lateral gene transfer is when an organisms of different species can acquire a gene from a different one. This process is well understood in bacteria and is responsible for the appearence of antibiotic resistant bacteria. Bacteria can take DNA fragments through a process known as transformation, but this is less common in eukaryotes. Gene transfer agents like viruses could carry the gene from one specimen to the other. Another way could be Horizontal transposon transfer but the exact mechanisms behind it are still under research.
An educated guess is the best way to describe hypothesis
Well it helped the animals and humans grow the population.
by the law of natural selection, daddy charles darwin stated that overpopulation could result in famine and wars, and death would accelerates across nations, so overpopulation is a cause for this because of too many organisms but not enough food, which declined growth rate.