The peak period for baby-making sex in ancient Egypt was in July and August, when the weather was at its hottest.

Researchers made this discovery at a cemetery in the Dakhleh Oasis in Egypt whose burials date back around 1,800 years. The oasis is located about 450 miles (720 kilometers) southwest of Cairo. The people buried in the cemetery lived in the ancient town of Kellis, with a population of at least several thousand. These people lived at a time when the Roman Empire controlled Egypt, when Christianity was spreading but also when traditional Egyptian religious beliefs were still strong.

So far, researchers have uncovered 765 graves, including the remains of 124 individuals that date to between 18 weeks and 45 weeks after conception. The excellent preservation let researchers date the age of the remains at death. The researchers could also pinpoint month of death, as the graves were oriented toward the rising sun, something that changes predictably throughout the year. [See Images of the Ancient Egypt Cemetery]

The results, combined with other information, suggested the peak period for births at the site was in March and April, and the peak period for conceptions was in July and August, when temperatures at the Dakhleh Oasis can easily reach more than 100 degrees Fahrenheit (40 degrees Celsius).

The peak period for the death of women of childbearing age was also in March and April (exactly mirroring the births), indicating that a substantial number of women died in childbirth.

Although attempts have been made in the past to piece together ancient Egyptian birth patterns using census records, researchers say this is the first time that these patterns have been determined by looking at burials.

"No one has ever looked at it using the actual individuals themselves, the biological aspects of it," said lead researcher Lana Williams, a professor at the University of Central Florida, in an interview with LiveScience.

The team presented their research recently at the annual meeting of the Society for American Archaeology in Honolulu.

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Sex in the summer

Conception didn't peak in summer months for other ancient Mediterranean cultures, Williams noted; the hot weather is thought to have lowered sexual libido and possibly sperm count.

In ancient Egypt, however, the new findings indicate that at Kellis conceptions increased by more than 20 percent above the site's annual average.

A summer baby-making boon in ancient Egypt may have been due to traditional beliefs regarding fertility and the Nile flood. The people who lived at the Dakhleh Oasis in ancient times believed that the Nile River was the source of their water and that the flooding of the Nile, which takes place in the summer, was key to the fertility of their land.

"Even though this was a Christian community, we know that they were still practicing, or having these social beliefs of, fertility being at its highest in the months of July and August," Williams said. "We have local temple reliefs that show this, the annual inundation of the Nile being celebrated at Dakhleh."

She added that the annual flood of the Nile River was a pivotal event throughout Egyptian history. "This was a very strong aspect of social beliefs of fertility," she said. "The Nile is the gift to Egypt — without it, there's really no way that this civilization could have survived through 3,000 years of history."

These patterns of conceptions and births would have likely continued back further into ancient times and occurred at other Egyptian sites as well, said Williams. In fact, they appear to have also continued into relatively modern times.

"Interestingly, all the way up into the 1920s and 1930s, we still see this maxima in birth taking place at the same season [around March and April]," Williams said in regards to birth records from the World Health Organization that looked at rural Egypt.

Sexual prohibitions

While the summer was prime time for ancient Egyptian baby-making, the period around January seems to have been a low point, when conception fell to 20 percent below the site's annual average. The baby dip was likely due to the new religion, Christianity, which in ancient times called for prohibitions on sex during certain periods, such as during Advent and Lent.

Ancient texts indicate that early Egyptian Christians were, ideally, supposed to avoid intercourse "on Saturday, on Sunday, on Wednesday, and on Friday, in the 40 days of Lent and before the other feasts at which they might take the Eucharist," writes Peter Brown, a professor of classics at Princeton University, in his book "The Body and Society: Men, Women and Sexual Renunciation in Early Christianity" (Columbia University Press, 2008 edition).

The people of Kellis may not have been as strict as these texts recommend, but conception did fall to a low point around January, a time close to both Advent and Lent, Williams pointed out.

Ancient contraceptives

The patterns also suggest some form of ancient contraceptives were in use. [The History & Future of Birth Control: 10 Contraceptives]

"If you have this much of a tightly patterned conception, there has to be some form of contraception that was taking place," Williams said, noting that ancient Egyptian medical texts tell of several methods that they believed acted to prevent pregnancy.

For instance, contraceptive recipes from the Kahun Medical Papyrus, dating back about 3,800 years, included crocodile dung and honey in their ingredients. It isn’t clear from the surviving papyrus exactly how they were to be inserted into the body. One fragment reads that for honey one was to "sprinkle [it] over her womb, this to be done on natron bed," (translation by Stephen Quirke).

Williams said that the prospect of having to take dung filled medicine, and having sex with it in you, probably discouraged intercourse. "By aversion alone, it would probably work for contraception," Williams said.

"The interesting thing is when you start to look at the ingredients, the high acid content that would be in crocodile dung, the anti-bacterial qualities of honey, it probably would take down the possibility of pregnancy by acting as a spermicide," said Williams, adding that it would not have been as effective as modern-day contraceptives.

Avoiding the taxman

When the team compared their research results with Roman census records, they found that the records were a bit off, indicating May and June as the time of maximum births.

As the census records were tied to taxation, the people living in Roman-controlled Egypt seem to have put off recording them.

"We don't want to pay our taxes until the last moment, so let's not do it, let's put off filing that document until we have to," said Williams, speculating on why they would have put off recording births. For the ancient Egyptians living under Roman rule, it seems sex, birth, death and taxes were all linked together.

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