Final answer:
The ancestral hominin that is technically us is Homo sapiens. Hominins include various groups that evolved after our lineage split from that of chimpanzees, and Homo sapiens is the only remaining species from that lineage.
Step-by-step explanation:
The ancestral hominin that is technically us is Homo sapiens, which is the species to which all modern human beings belong. Before Homo sapiens, there were several hominin groups considered to be part of the direct human lineage, including Australopithecus, Homo habilis, and Homo erectus. However, Homo sapiens is the only surviving species from this lineage. Our ancient cousins such as the Neanderthals and Denisovans, despite sharing common ancestors with us, are not technically Homo sapiens but are closely related and at times even interbred with our lineage.
The term 'hominin' encompasses all human ancestors that evolved after the hominin line diverged from that of chimpanzees about 6 million years ago. These included species from the genera Homo, Australopithecus, Paranthropus, and Ardipithecus. Hominins share key characteristics such as bipedalism, larger brains, reduced jaw protrusion, and opposable thumbs. Fossil evidence from various hominins exhibits a progression towards the modern human form over millions of years. The Australopithecines, for example, had a smaller brain size than modern humans and a more pronounced jaw, as seen in the structure of their skulls. The discovery of these early hominins and their evolved traits have been pivotal in understanding the journey of human evolution.