A recent study of tens of thousands of birds has shown that birds are growing smaller over time. It could be due to climate change, and if so, we ought to consider: How else might humans be altering the literal shape of life on Earth — now and in the future? For more, go to http://vox.com/unexplainable It’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.com We read every email. Support Unexplainable by making a financial contribution to Vox! bit.ly/givepodcasts Learn more about your ad choices. Visit podcastchoices.com/adchoices