To begin to explain this, we turn to Nina Jablonski, professor of anthropology at Pennsylvania State University. She is a well-recognized researcher in primate evolution, and specifically the evolution of human skin, and she was the subject of a Science Seat on CNN Light Years.

COLUMBUS, OHIO (CNN) -- President Obama told graduates Sunday that "the institutions that give structure to our society have at times betrayed your trust" but called on young people to take a more active role in the political process as part of the solution.

Rhode Island became the tenth state in the nation to legalize same-sex marriage after the state legislature approved the measure on Thursday. Gov. Lincoln Chafee is expected to sign the bill at 5:45 p.m. ET.

Rep. Ed Markey, who became the Democratic nominee for U.S. Senate in Massachusetts earlier this week, will get a boost later this month from first lady Michelle Obama, who will travel to the state for a fundraising event.

Two years into the civil war that has become Syria's nightmare, U.S. President Barack Obama is still reluctant to commit himself to ending the carnage or even enforce his own warning about chemical weapons.

WASHINGTON (CNN) -- Calling him the "Bo Jackson of telecom" for his membership in both the cable television and wireless industries' halls of fame, President Obama announced plans Wednesday to nominate Tom Wheeler to head the Federal Communications Commission.

WASHINGTON (CNN) -- President Barack Obama filled out his Cabinet nominations Thursday morning when he tapped Penny Pritzker as his commerce secretary and Michael Froman as his U.S. trade representative.

(CNN) -- A Kentucky mother stepped outside of her home just for a few minutes, but it was long enough for her 5-year-old son to accidentally shoot and kill his 2-year-old sister with the .22-caliber rifle he got for his birthday, state officials said.

President Barack Obama said Tuesday that he continues to believe that the United States should close the detention facility at Guantanamo Bay, Cuba

Republican Sen. Marco Rubio said Tuesday he doubts the so-called Gang of Eight's bipartisan immigration reform will gain enough support in the GOP-controlled House of Representatives.