# Science Spotlights: Why Do We Walk on Two Legs? Ask a Leaf! ![Woman with a hat on looking at the camera](/sites/g/files/omnuum4986/files/styles/hwp_5_4__480x385/public/2025-10/11-22%20Sci%20Spotlight%20Tweedy%20detail.jpg?itok=cUaPrxvq) #### calendar\_today Date and Time **November 22, 2025** 02:00PM - 02:30PM EST #### pin\_drop Location **Harvard Museum of Natural History** [26 Oxford Street Classroom B (Third Floor) Cambridge, MA 02138 United States ]() **In-Person Presentation** **Speaker:** Ruth Tweedy, Graduate Student, Department of Earth and Planetary Sciences Meet up-and-coming scientists and learn about questions at the forefront of research today in this series of short talks. **2:00–2:30 pm Why Do We Walk on Two Legs? Ask a Leaf!** Have you ever wondered why people walk on two legs, while monkeys and apes—our closest living relatives—still swing through trees? Harvard scientist Ruth Tweedy thinks the answer might have something to do with where early humans lived. She studies ancient landscapes in eastern Africa by looking at the waxy coatings on leaves—tiny chemical “fingerprints” that plants leave behind in the ground. These fingerprints can last for millions of years and help tell the story of what the world looked like long ago. Join Ruth to uncover how clues from leaves reveal the environments where early humans lived—and why standing tall might have been the smartest way to get around. Recommended for ages 10 and up. Regular museum admission rates apply. Presented by the Harvard Museum of Natural History and Harvard Museums of Science & Culture. Share on:- [ Facebook ](#) - [ Twitter ](#) - [ Linkedin ](#) Save: [ Add to calendar calendar\_today ](https://www.hmnh.harvard.edu/node/1616981/event-feed.ics) Copy link link