What science knows it doesn't know

Scientific journal Science is celebrating its 125th anniversary by asking 125 big questions that science can't answer... yet. The ground rule in the selection process was that "scientists should have a good shot at answering the questions over the next 25 years, or they should at least know how to go about answering them." Here are the top 25:
What Is the Universe Made Of?
What is the Biological Basis of Consciousness?
Why Do Humans Have So Few Genes?
To What Extent Are Genetic Variation and Personal Health Linked?
Can the Laws of Physics Be Unified?
How Much Can Human Life Span Be Extended?
What Controls Organ Regeneration?
How Can a Skin Cell Become a Nerve Cell?
How Does a Single Somatic Cell Become a Whole Plant?
How Does Earth's Interior Work?
Are We Alone in the Universe?
How and Where Did Life on Earth Arise?
What Determines Species Diversity?
What Genetic Changes Made Us Uniquely Human?
How Are Memories Stored and Retrieved?
How Did Cooperative Behavior Evolve?
How Will Big Pictures Emerge from a Sea of Biological Data?
How Far Can We Push Chemical Self-Assembly?
What Are the Limits of Conventional Computing?
Can We Selectively Shut Off Immune Responses?
Do Deeper Principles Underlie Quantum Uncertainty and Nonlocality?
Is an Effective HIV Vaccine Feasible?
How Hot Will the Greenhouse World Be?
What Can Replace Cheap Oil -- and When?
Will Malthus Continue to Be Wrong?