Marines finish a 10 kilometer training hike carrying 55 pound (25 kg) packs during Marine Combat Training (MCT) on February 22, 2013 at Camp Lejeune, North Carolina. Since 1988 all non-infantry enlisted male Marines have been required to complete 29 days of basic combat skills training at MCT after graduating from boot camp. MCT has been required for all enlisted female Marines since 1997. About six percent of enlisted Marines are female. (Photo by Scott Olson/AFP Photo)

An Israeli Air Force F-35 fighter jet flies during an aerial demonstration at a graduation ceremony for Israeli airforce pilots at the Hatzerim air base in southern Israel December 29, 2016. (Photo by Amir Cohen/Reuters)

Police academy graduates march during their graduation ceremony in Islamabad, Pakistan May 18, 2015. Out of the 408 graduating officers, 76 female officers were inducted into the Pakistan police force, according to the police force. (Photo by Caren Firouz/Reuters)

As the world marks International Women's Day on Wednesday, whose theme this year focuses on “women in the changing world of work”, the Israeli military says it is ahead of the curve in providing combat roles for female soldiers. Here: A female Israeli soldier from the Haraam artillery battalion fixes her hair in the women's living quarters at a military base in the Israeli-occupied Golan Heights March 1, 2017. (Photo by Nir Elias/Reuters)

Ayesha Farooq, 26, Pakistan's only female war-ready fighter pilot watches an airforce jet about to take off at Mushaf base in Sargodha, north Pakistan June 7, 2013. Farooq, from Punjab province's historic city of Bahawalpur, is one of 19 women who have become pilots in the Pakistan Air Force over the last decade – there are five other female fighter pilots, but they have yet to take the final tests to qualify for combat. A growing number of women have joined Pakistan's defence forces in recent years as attitudes towards women change. (Photo by Zohra Bensemra/Reuters)

A Libyan rebel fires on a government jet as a natural gas facility burns on the frontline on March 9, 2011 near Ras Lanuf, Libya. The rebels pushed back government troops loyal to Libyan leader Muammar Gaddafi towards Ben Jawat.

Libyan rebel fighters protect a pro-Gaddafi loyalist fighter from angry onlookers as he is brought in for medical attention to the Tripoli Central Hospital on August 25, 2011 in Tripoli, Libya. Heavy fighting continues in the Libyan capital between Gaddafi's forces and the surging rebel presence. Rebels, who have issued a $1.7m reward for Gaddafi's capture “dead or alive”, are attempting to reach Colonel Gaddafi's hometown of Sirte but have met loyalist resistance. (Photo by Daniel Berehulak/Getty Images)

FaceResearch.org, a site run by two psychologists at the University of Aberdeen in Scotland, features software that can average together faces from thousands of photos. These images purportedly show the average face of women from 40 different nationalities.