Population

Estimated population of Europe in 1492: about 60 million
Estimated population of the Americas in 1492: 40–100 million

Estimated population of Europe in 1800: 150 million
Estimated population of the Americas in 1800: 25 million (the vast majority of whom were of European or African descent)

Animals

Major domesticated animals in the New World in 1492: dog, llama

Major domesticated animals in the Old World in 1492: horse, cow, pig, sheep, goat, chicken, camel, oxen, cat, dog

Plants

Major edible plants unique to the New World in 1492: maize (corn), potato, squash, cassava (manioc), tomato, bell pepper, chili pepper, avocado, squash, pumpkin, peanut, chocolate, vanilla, strawberry, blueberry, pineapple, tobacco

Major edible plants unique to the Old World in 1492: wheat, oats, barley, lettuce, onion, garlic, banana, orange, lemon, peach, sugarcane, coffee, tea

When Old and New Meet

Estimated number of Incas killed by smallpox between 1525 and 1532, when Francisco Pizarro conquered the empire: more than 200,000¹

Estimated proportion of the Aztec population of Tenochtitlan infected by smallpox in 1520, one year before Hernán Cortés conquered the empire: 50%²