But little direct evidence exists to prove which tree species filled the forests before they were cleared for fields and fuel. (scientificamerican.com)
Many researchers agree that shifts in climate and environment shaped human evolution, but there has been little direct evidence about exactly how. (science.sciencemag.org)
But little direct evidence of Hadean asteroid impacts still exists, limiting scientists» understanding of how those collisions affected the planet's habitability. (sciencenews.org)