Basic biology has it that girls are girls because they have two X chromosomes — the things inside cells that carry our genes. Boys are boys because they have one X and one Y. Recently, though, there's been a lot of debate in scientific circles about the fate of that Y chromosome — the genetic basis of maleness.
One hundred years ago today, the Austro-Hungarian Empire declared war on Serbia. The conflict drew in country after country and grew to an unprecedented scale. An estimated 9 million combatants lost their lives and more than 21 million were wounded in what came to be known as The Great War and, eventually, World War I.