Charles Darwin’s sketch of how species are related is a tad messy, so I simplified the lines and I nudged the “I think” notation to a different location. You can get laptop stickers, t-shirts, etc. at my Redbubble site. E.g., here’s a sticker. For dark t-shirts and such us this link.
If you’re not a fan of the “I think” text, here’s the sketch-only version.
By the way, I originally created this design in 2009 for temporary tattoos.