The first fossils that paleontologists classify as members of our genus, Homo, was Homo erectus about 1.8 million years ago. Recent fossil finds indicate they hung around until at least 143,000 years ago, which means they overlapped with Homo sapiens, our species.
A word about genera (plural of genus) and species. A group of plants or animals that look alike and interbreed freely are considered a species. If the genes of members of a species are sequenced, those genes are pretty similar within a species. Members of one species don’t usually interbreed with another species. Horses (Equus ferus) and donkeys (Equus asinus) are a good practical example. In nature, they don’t interbreed. When we interbreed them to produce mules or hinnies, the offspring of the union is big and strong, but sterile because key elements of their genome differ. Notice that the horse and donkey are in the same genus, Equus. The recent findings that we share some genes with Homo neanderthalensis, Neanderthal Man, shows we could still interbreed.
Here’s the Smithsonian Institution’s Tree of Life for our lineage of primates– http://humanorigins.si.edu/evidence/human-family-tree. A recent find and analysis claims some of the species listed under Homo were actually Homo erectus.