Some believe humans have been on the planet for 6 million years. If that seems a long time, consider dinosaurs, which inhabited Earth for 165 million years before their demise. Now think about what remnants of dinosaurs have survived the millennia. Imagine all humans vanished in 50,000 years, only archaeological traces would remain and then radioactive materials and few man-made chemical contaminants would last longer- although some guess Twinkies and cockroaches would contribute to the legacy. Fields would be overgrown with weeds in months. In 20 years, village streets and rural roads would be covered by a matting of weeds.
City streets and roads would vanish in about 50 years. Wooden structures would collapse within a century under attack from insects. Glass and steel structures would fall within 200 years, but stone and brick would last a bit longer. After 3000 years, only ruins would survive. Wildlife would thrive with out the threat posed by humans. Most of the 15,589 threatened species would immediatly begin a return to historical populations. Carbon dioxide would continue to cause climate change for a century, but after 1,000 years would return to preindustrial levels. After 20,000 years, all man-made traces would vanish. Radioactive untreated nuclear waste could linger for two million years. If an alien archeologist landed on Earth in 50,000 years, he might have great diffuculty finding evidence that humans ever exsisted.-emt
