Identify three groups most scientists consider to be direct ancestors of modern humans.

Homo erectus evolves in Africa. Homo erectus would bear a striking resemblance to modern humans, but had a brain about 74 percent of the size of modern man. Its forehead is less sloping than that of Homo habilis and the teeth are smaller.
Homo antecessor may be a common ancestor of humans and Neanderthals.] At present estimate, humans have approximately 20,000–25,000 genes and share 99% of their DNA with the now extinct Neanderthal [ and 95–99% of their DNA with their closest living evolutionary relative, the chimpanzees. The human variant of the FOXP2 gene (linked to the control of speech) has been found to be identical in Neanderthals.
Homo heidelbergensis left footprints in powdery volcanic ash solidified in Italy. Homo heidelbergensis may be a common ancestor of humans and Neanderthals. It is morphologically very similar to Homo erectus but Homo heidelbergensis had a larger brain-case, about 93% the size of that of Homo sapiens. The holotype of the species was tall, 1.8 m (6 ft) and more muscular than modern humans.

They are both used to view parts of the cell