The most commonly used evidence of fire is remnants of charcoal, burned earth, or burned bone, that can either be dated directly, or dated in relation to objects of known age nearby. The chief issue with the extremely early dates for fire use (>600,000 years ago) often associated the H. erectus is that the evidence of those fires is difficult to distinguish from naturally occurring brush or forest fires. After several hundred thousand years a burning stump and an intentionally managed, but not re-used, cooking spot tend to look the same. Richard Wrangham is perhaps one of the most vocal advocates for the early appearance of fire, and he maintains cooking drove cognitive, social, and biological changes in our genus that eventually prompted the emergence of anatomically modern H. sapiens. His detractors claim the early hominin use of fire vs. naturally occurring processes isn't clear enough, nor is there sufficient evidence of early consistent, controlled use of fire needed to cook foods (and drive evolutionary change in our species).

By ~200,000 years ago, hominins begin constructed hearths, and routinely re-use cooking space, which leaves much better evidence of consistent, controlled use of fire. If you are interested in Wrangham's work Catching Fire: How Cooking Made us Human is an accessible introduction into the fire and cooking debate.

Hi, questions on early humanoids are worth x-posting to our sister sub /r/AskAnthropology