Yeah, you’ve probably heard it before: We’re in the middle of a massive extinction era on a par with the one that wiped out the dinosaurs 65 million years ago — only this one is our own doing. By the middle of this century, human activities will have erased up to 30 percent of all species on Earth, according to many biologists. Many of those species will have come and gone without so much as a blip on the human radar screen, meaning their ecological role and potential usefulness to people will remain forever unknown. In an effort to minimize the number of species that fall into that mystery category, scientists are undertaking a massive effort to create a comprehensive “family tree” of life on Earth — from wooly mammoths to itty-bitty bacteria. The projects’ backers say it will help scientists understand how organisms function within their niches, shed light on evolution, and even help track acts of bioterrorism. The project is being funded by the National Science Foundation to the tune of $10 to $12 million per year and could take up to 15 years to complete.