Over 1.9 million years ago, human beings were still having dinner dates, according to a recently published article by Professor of Anthropology Richard W. Wrangham.

The article, published in the December issue of Current Anthropologist, hypothesizes that at this time humans first harnessed fire for cooking.

The first use of fire brought great changes to the human social structure, Wrangham said.

With the advent of cooking, the article argues, human beings moved from a " hunter/gatherer" existence to a "producer/scrounger" social structure.

"Before, people lived like apes--everybody fed himself," Wrangham said. "[With] cooking, it became worthwhile to bring food in large quantities to a central location, and the concepts of ownership and theft came into existence."

Females often found themselves victims of theft from the larger males. As a result, it was advantageous for a female to align herself with a male interested in protecting their mutual food stores--hence the modern-day couples.

"The male fought off thieves in exchange for sex and hot food. It's a protection racket, really," he said.

Females selected stronger males. In return, males selected more sexually attractive females. It is possible this resulted in hidden ovulation--women, unlike other mammals, do not show external signs of ovulating.