What condensed matter physics is not the same
thing as solid state physics. Solid state physics is the study of, say,
electrons in metals like insulators, semiconductors, super conductors and so on. But what condensed matter physics is, is it
goes beyond the behavior of individual components to see how they self organize in some kind
of collective state. In other words, the behavior of the collective
is much more important than the behavior of the individual. An example that everyone's familiar with is
a flock of birds. Every bird is flying around. They, in principle, can fly in any direction. But in a flock they all fly together in some
cohesive way. Another example in physics is just atoms. If you push air or push water, your finger
just goes straight through it. But if I take this book and I push it, my
finger doesn't go through it. It just moves. I can transmit a force. That's because the atoms in it have self organized
into some collective state. Rather than just do their own thing, they
all move together. It's a kind of conspiracy of atoms, if you
will. Now, turning to biology — the big puzzle
in early evolution is this: The planet started about 4.6 billion years ago. We know that the last universal common ancestor
of all life was about 3.8 billion years ago. That's the organism from which all life on
Earth is descended, or maybe a community of organisms. Now, we know that because we can look at genes
in modern cells, genes that code for the machinery that makes proteins. That machinery we can trace back by undoing
the process of evolution, if you will, back to about 3.8 billion years ago. What that means is that the modern cell had
already evolved, more or less, with it's current complexity, 3.8 billion years ago. The planet is 4.6 billion years. So we went from nothing to the complexity
of the modern cell in less than a billion years. And after that evolution didn't do that much. So how is it possible that evolution started
off so fast and then later on made many evolutionary changes but nothing fundamental to the architecture
of the cell? Well the answer that we've proposed is that
it was, in fact, collective effects. Today, genes are transmitted from one person
to the other, and that person has to be their descendant. Everyone is familiar with a family tree. But what we discovered is that if we assumed
that early on in life genes are transmitted between individuals, even if they're not related
— this is called horizontal gene transfer — we get not a tree of life, but a network
of life. And the network grows exponentially fast. Just like how the Internet grew very quickly
in the mid-1990s, because you had a network effect. All the computers in the world could talk
to one another. The understanding of condensed matter physics
enabled us to really understand how we could model the collective behavior of organisms
that could transfer genes. What we able to show was that the properties
of the genetic code that emerged from that would agree with what we see today. If we assumed just a regular tree of life
behavior — no network effect — we couldn't explain the speed of life, the speed at which
evolution occurred. We couldn't explain the fact that every organism
has the same genetic code. We couldn't explain the fact that the genetic
code is remarkably robust to ours. In short, then, condensed matter physics does
have applications in biology because biology is all about collective effects. It's a wonderful testbed for understanding
ideas of condensed matter physics, but in a more broader sense, the idea of strongly
interacting collective properties of matter.
