Study Offers Earliest Evidence of Humans Changing Ecosystems with Fire The artifacts examined by the researchers are of the type produced across Africa in the Middle Stone Age, a period dating back at least 315,000 years. (Yale University) Baylor University paleoclimatologist Steven Forman, Ph.D., was one of 27 researchers involved in a Yale-led study published in the journal Science Advances that provides the earliest evidence to date of ancient humans significantly altering entire ecosystems with flames. Researchers show archaeological evidence â dense clusters of stone artifacts dating as far back as 92,000 years ago â discovered on the northern shores of Lake Malawi in eastern Africa. (Yale University)