The consequences of climate change, the birth of the universe and the science of kissing are among the topics set to be explored at a top scientific conference that opens Thursday in Chicago.
As many as 10,000 researchers from across the globe are expected to attend the annual meeting of the American Association for the Advancement of Science (AAAS), which runs through Monday.
The conference theme, "Our Planet and its Life: Origins and Futures" was chosen in recognition of the 200th anniversary of Charles Darwin's birth and the 150th anniversary of the publication of his book "On the Origin of the Species."
"New understanding of the processes that fascinated Darwin continues to be the focus of intense research 150 years later," said James McCarthy, president of the AAAS and a Harvard professor.
"Indeed every discipline can demonstrate its own unique evolutionary path and speculate on where it may lead."
From the origins of life to how animals use their own odors to avoid inbreeding, evolution is the focus of a number of the more than 150 symposiums and 36 press conferences.
Kissing will be explored from its social implications in ancient Greek and Rome to the chemicals and hormonal changes unleashed in the body through the locking of lips, which have the thinnest layer of skin of any part of the body and are densely packed with sensory neurons.
Svante Paabo, director of genetics at the Max Planck Institute for Evolutionary Anthropology, will present the most comprehensive results of his team's effort to sequence the entire genome of the Neanderthal.
Other researchers will present their findings on the role of women in natural selection and the transfer of social information.
The complex chemistry that allows for life to form, the origins and evolution of the planets, and the possibility of undiscovered life on Earth will also be explored.
The consequences of climate change is another major theme as researchers present findings on disappearing Arctic sea ice, the collapse of fisheries, the spread of disease, and how the push for biofuels could make matters worse instead of better.
Former US vice president Al Gore, who won the Nobel Prize for his work on climate change, is invited to speak on Friday.
The conference will also recognize the 150th anniversary of the first drilling of a commercial oil well with a symposium examining how cheap oil shaped our economy and society, and what the transition away from a petroleum-based economy could look like.
Astronomers will mark the 400th anniversary of the birth of their field by reexamining Galileo's discoveries and discussing the hundreds of new planets being found in recent years, which challenge basic notions of planetary formation and structure.
Food and water are also the topics of much discussion as researchers examine the dwindling supply of potable water, ways to prevent food riots, the safety of food imports, and the truth behind the hype of how food can help prevent disease.
New data on the links between poverty, crime and race will also be presented, as will fresh research on the impact of post traumatic stress disorder in the military.