Final answer:
The first species known to practice intentional burials were the Neanderthals, as evidenced by the careful placement of bodies and the probable presence of flowers in graves like those found at the Shanidar 4 site in Iraq.
Step-by-step explanation:
The earliest evidence we have of intentional burials comes from the Neanderthals, a close relative to modern humans. The site known as Shanidar 4 in Iraq has provided significant evidence to support this, where an individual was carefuly laid to rest in a flexed position, and pollen analyses suggest the presence of flowers, potentially indicative of a ritualistic or ceremonial burial practice. While some alternative hypotheses exist, such as the pollen being the result of rodents' activity, the consensus supports the intentional placement of the body in a grave, supporting the practice of ritual burials by Neanderthals. In addition to Neanderthal burials, evidence of increasingly complex burials in human history often correlates with the growth of social hierarchy and inequality, as seen in various cultures such as Neolithic communities in the Yellow River area around 4500 BC.