For example, did our supposed ancestors create these sharpened pieces of obsidian? If so, why do we think that these members of the genus Homo, specifically H. heidelbergensis, are actually ancestral to our species? Why are sapiens and heidelbergensis separated into different species anyway?
The answer one usually hears is that heidelbergensis is morphologically different, though not much, from modern humans, and if one assumes an evolutionary progression it makes sense to think that they were the species that eventually evolved into H. sapiens.
This reasoning, though, is questionable. The biological definition of a species is a reproductively isolated population of organisms. That is, if a certain population of creatures cannot interbreed with members of other populations and produce fertile offspring the two groups are considered taxonomically distinct species.
But how do we know that H. heidelbergensis could not interbreed with H. sapiens? Morphological differences are hardly a reason for thinking that they couldn't. After all, there's far more morphological variation among the different breeds of dogs, but every one of them is a member of the same species.
Maybe there are really just two kinds of hominids: Men and apes, and any attempt to draw arbitrary and hypothetical gradations between them is simply an attempt to find an evolutionary connection that isn't there.
Here's the lede from the story of the spearheads:
Remains of the oldest known stone-tipped throwing spears, described in a new paper, are so ancient that they actually predate the earliest known fossils for our species by 85,000 years.Could it be that the human species - our species - actually has no true ancestral hominid precursors? If it should ever turn out that that's the case, it would throw Darwinian explanations of human evolution, already tenuous enough, into a tailspin.
There are a couple possible implications, and both are mind-blowing. The first is that our species could be much older than previously thought, which would forever change the existing human family tree.
The second, and more likely at this point, is that a predecessor species to ours was extremely crafty and clever, making sophisticated tools long before Homo sapiens emerged.
Homo heidelbergensis, aka Heidelberg Man, lived in Africa, Europe and western Asia from at least 600,000 years ago. He clearly got around, and many think this species was the direct ancestor of Homo sapiens in Africa and Neanderthals in Europe and Asia. The new paper, published in the latest PLoS ONE, focuses on the newly identified stone-tipped spears, which date to 280,000 years ago. They were found at an Ethiopian Stone Age site known as Gademotta.
....the spears were made from obsidian found near the site. The toolmakers had to craft the pointy spearhead shapes and spear shafts. They then needed to attach the points securely to the shafts. Even today, all of this would require skill, concentration and multiple steps.