When scientists examined the DNA of ancient bones found near a Himalayan lake, they were forced to confront a seemingly impossible conclusion.*This episode has been updated. In the original version, we mixed up carbon isotopes with carbon isotope ratios.For further reading, go to http://vox.com/unexplainableIt’s a great place to sign up for our newsletter, view show transcripts, and read more about the topics on our show.Also, email us! unexplainable@vox.comWe read every email. Learn more about your ad choices. Visit podcastchoices.com/adchoices

Sixty years ago, geologists tried to drill down through the Earth’s crust to pull up a piece of the Earth’s mantle. Their mission didn’t go exactly as planned. But it sowed the seeds for a new field of science that’s helped us rewrite not only the history of the planet, but, potentially, our definitions of life itself.The documentaries featured in this episode are "The First Deep Ocean Drilling: Mohole, Phase 1" and "Project Mohole: Report No. 1."For further reading, sign up for our newsletter here: http://vox.com/unexplainable-newsletterShow transcript and articles at: http://vox.com/unexplainableEmail us! unexplainable@vox.comWe read every email. Learn more about your ad choices. Visit podcastchoices.com/adchoices

Believe it or not, scientists still don't know how the sense of smell works. But they're looking at how powerful it is - dogs can actually sniff out cancer and many other diseases - and they're trying to figure out how to reverse engineer it. In fact, one MIT scientist may have built a robot nose ... without completely understanding how his invention works.For further reading, sign up for our newsletter here: http://vox.com/unexplainable-newsletterShow transcript and articles at: http://vox.com/unexplainableArticle on quantum nose theory: https://bit.ly/3clurfsEmail us! unexplainable@vox.comWe read every email. Learn more about your ad choices. Visit podcastchoices.com/adchoices

Scientists all over the world are searching for dark matter: an invisible, untouchable substance that holds our universe together. But they haven't found it. Are they chasing a ghost?For further reading, sign up for our newsletter here: http://vox.com/unexplainable-newsletterShow transcript and articles (including one about why we made this show now): http://vox.com/unexplainableEmail us! unexplainable@vox.comWe read every email. Learn more about your ad choices. Visit podcastchoices.com/adchoices

Scientists don’t know what 95% of the universe is made of. They don’t know how a bike stays up. They don’t even really know how the nose works. Join us every Wednesday on Unexplainable for deep dives into the unknown, because what we don’t know is awesome. New episodes March 10th. Learn more about your ad choices. Visit podcastchoices.com/adchoices