How did the Columbian Exchange impact the Americas? a- New technologies such as tools made of metal and guns, were introduced into the Americas.
b- Groundbreaking medical knowledge resulted in longer lives for native people,
c- Corn was introduced as a food source in the Americas, resulting in population growth.
d- The population of the Americas decreased as native people moved to Europe.

i believe the answer is a

its many islands, high mountains, and remote peninsulas isolated population centers.

donald carl johanson (born june 28, 1943) is an american paleoanthropologist. he is known for discovering – with yves coppens and maurice taieb – the fossil of a female hominin australopithecine known as "lucy" in the afar triangle region of hadar, ethiopia.

hope this !

i googled "who was kolson johanson" and this is the answer i found.

sorry if this is incorrect.