Happy #Thanksgiving! I'm #thankful for many things, including #biology's grand unifying #theory, which made its debut in printed form this date in 1859 when Charles #Darwin published #OnTheOriginOfSpecies. Pictured are some of the lines of evidence that made his work possible: #pigeons that Darwin kept and raised, #mammal #fossil he collected in #Uruguay (both from #London's #NaturalHistoryMuseum), and carnivorous #plants from his #greenhouse at his home, #DownHouse, in #Kent.