CAPTCHAs were created in the early 2000s to distinguish humans from bots by having users type distorted text. Over time, CAPTCHAs evolved from static text to using images from books and street signs to aid in digitization. As AI advanced, CAPTCHAs became easier for bots to solve, so Google introduced "No CAPTCHA reCAPTCHA" using online behavior analysis rather than text. The ongoing arms race between CAPTCHAs and improving AI means new techniques are constantly needed to tell humans and bots apart.