While one can not truly just jump into the past and see previous human activity, Archaeologists can study the remains left over. There are also other scientist that can observe tracks and enviornment to determine human activity, but the name I can not recall at the moment.
acosil csesitnti
That would be an anthropologist.
A cultural Anthropologist, though I would not call them scientists.Perhaps a Sociobiologist or a Human Behavioral Ecologist would be more scientifically inclined here.
oceanagrapher
A geographer would study the physical features of an area and how they relate to politics, economy, and archaeology. A political scientist would study the structure and functions of political systems in different regions. An archaeologist would study past human cultures and societies through material remains. An economist would study the production, distribution, and consumption of goods and services in different regions.
A microbiologist.
hyponism :)
An archaeologist would most likely study artifacts found in ruins as they are trained to uncover, analyze, and interpret material remains from past human societies.
A paleontologist would generally study paleontology.
a physicist
An astronomer.
Volcanologist.