5 Most Incredible Discoveries of the Week Including a study suggesting that we peak at age 24 By Newser Editors, Newser Staff Posted Apr 19, 2014 5:20 AM CDT 0 comments Comments This artist's rendering provided by NASA shows an Earth-sized planet dubbed Kepler-186f orbiting a star some 500 light-years from Earth. (AP Photo/NASA Ames, SETI Institute, JPL-Caltech, T. Pyle) (Newser) – The most Earth-like planet discovered yet, and a bizarre finding in the insect world make the list: Astronomers Find Earth's 'Cousin': Other "Earth-like" planets have been discovered before, but a new one is generating excitement in astronomy circles because of how very Earth-like it actually is. Introducing Kepler-186f, which is maybe 10% bigger than our planet, orbits a sunlike star, and is thought to be in the not-too-hot and not-too-cold range that would make water—and life—possible. Under Greenland's Ice: Soil Older Than Mankind: The soil under the highest point of the Greenland Ice Sheet, scientists have learned, is 2.7 million years old. In other words, the silt buried under thousands of feet of ice "has been preserved from beyond the dawn of humankind," says one. What's more, younger Greenland looked very different from the one we know today. Wild Discovery: Insects With Female Penises: For the first time, scientists have discovered animals whose genitalia seem to be swapped: The female has a penis-like structure while the male has an organ akin to a vagina. The animals in question are four species of flea-sized insects from found in Brazilian caves, and the surprises don't end with mere physical differences. Study: Cherokee Struggles Visible in Their Skulls: It turns out the Trail of Tears didn't just affect the Cherokee people's spirits. A new study by North Carolina State University and University of Tennessee researchers has found that their struggles actually reshaped their skulls. Study: We Peak at Age 24: If you're over the age of 24, Simon Fraser University researchers have some gloomy news for you. As the Canadian school's press release puts it, "Study says we're over the hill at 24." The statement stems from a new study on cognitive motor performance. Click for more discoveries, including a new Saturn moon.