This book is everything. Historically, humans have treated physics and biology as if they are completely separate. That is not because scientists and the rest of society are stupid. It is because trying to understand our world, understand the universe outside our world, and how the laws of physics govern both is a very difficult task and has taken centuries of human understanding to even achieve the little we know at present. The field of astrobiology is a relatively new one specifically because it took us this long to start to fit together the pieces of the puzzle that explain how physical forces act upon and constrain the Endless Forms Most Beautiful that evolve upon Earth . In his book life equations Cockell described how the physical laws that govern the entire universe are at work here on Earth to shape and sustain the life we see before our eyes. Understanding what is in this book is the only way to understand the progressing theory of evolution. Though he doesn't necessarily name the people I list here, he most certainly covers the work of researcher such as Nick Lane (hydrothermal vents/thermodynamics and energetics of evolution), Jeremy England (dissipation of energy, adaptation of systems), biologist Sean Carroll (who he does name when he describes HOX genes), David Deamer (first life research). He is no dummy about the politics of science; he makes sure to dismiss Dawkins while still treating him with kid gloves.
This book is definitely a must read for anyone interested in the theory of evolution and how researchers are finally connecting the dots from biology to physics. One day we will laugh at a statement like that and say, 'Duh, of course the laws of biology conform to and are constrained by the laws of physics. How could anyone have thought otherwise?" It is just the case that it has taken centuries of scientific investigation to get to this point of understanding. Much of what is written here will seem like it must not be new. After all, it is so intuitive. While a lot of this work is many decades in the making, what is in this book is decidedly new because it took this long to be able to say all of this without too much controversy. What is written down in these pages is what we finally understand about how the laws of physics formed life, constrained the size and shape life could take, dictate the shape and number of the building blocks that were used to create Darwin's endless forms (Cockell will tell you why they are not truly endless), why the metabolism of all life uses the mechanisms it does, and what extreme conditions make it impossible for any life (as defined through a biological lens) can exist at all.
The central message for the reader is, life is math; you simply have to know how to understand the equations. The evolution of forms, life, death, and activity of the evolved forms all have equations, and these equations interact with other equations. No matter the interaction, no matter how vast forms and behaviors of forms seem to be, every single equation is bound by the laws of physics. Despite the title, the book itself included relatively few equations and focused more on discussing why we should try to understand the equations of life.
What are the equations for moving through water or walking on land? Why does it even matter? What would it tell us? It actually tells us a lot. If we can begin by understanding how simple forces like gravity (funny to call it simple since that force is one of the most complex issues in physics today) can pull something inward (or more accurately, make something roll down a hill toward it), we can understand something about the formation of stars and planets, as well as gain an understanding of our wider universe. But, what forces are at work when a small lady bug climbs up a wall? The tiny bug isn't very affected by gravity. Along with a weak force of gravity, the molecular forces of Van der Waals bonds are at work on the tiny, building climbing bug. How did that lady bug come to exist on the land and not exist as a fish in water, which allows animals to be less constrained by the forces of gravity? How did even larger animals, like big boned elephants, large horses, or humans evolve to withstand the pressures gravity exerts on land dwelling creatures? What are the equations that could help us understand how bones and skin need to change in order for fish to evolve and climb out of the water and, over time, evolve limbs that allow it to walk on land and bones thick enough to withstand the 9.8 meters per second squared gravitational force pushing down on it? What are the equations that govern the evolution of thickening skin, which now has to do the job of absorbing highly energetic UV rays from the sun that the water used to absorb? In order to avoid cell damage fungi, plants, and animals had to develop pigment, such as melanin, to help fend off some of that cancer causing energy. In addition to needing pigment, skin that exists on land has to be able to trap water inside. Your ancestors might have left the water, but if they didn't put water back inside their bodies very often and trap that water in a nice thick membrane of skin, they would have become dehydrated and died.
What are the equations that constrain the extreme boundaries for the existence of any form of life? One thing we can look at is temperature. Extreme temperatures around earth make it difficult for life forms to take shape or remain active. For example, organisms can live at -50 degrees C, but everything runs so slowly. A slow metabolism means that a cell cannot repair itself fast enough from normal cellular damage. At Earth's poles, such as Antarctica, temperatures are so cold, it freezes the fatty acids that make up the cell's membrane. A frozen membrane causes a cell to starve to death. The frozen, rigid fatty acid membrane cannot open up and take in nutrients (like oxygen, carbon, etc). To make their membranes a bit more flexible, some cells have evolved a single modification that allows the fatty acid to form a double bond instead of the normal single bond. That double bond is life saving because it allows cells to gain enough flexibility to open their mouths (channels) and take in food and air (oxygen, carbon, etc). Imagine your nostrils and mouth being frozen shut but then someone pokes a tiny hole in one of your openings and lets you breath air, drink water, or ingest food. Reading this section, funny enough, made me think of a show I saw when I was young, which horrified me. A girl was abducted and buried under ground, with only a thin tube through which to breathe. That tv show really stuck with me. When I read about the poor cells in Antarctica, I could not help but think about the girl who was buried and partially suffocated. (Weird thing to relate, I know.) Conversely, if temperatures are too high, even the fastest metabolizing cells cannot move fast enough to repair damage because that much heat causes damage on a continual basis. Life exists only on a thin layer on the planet. Even if we could extend the boundary of life to 450 C, we could triple the thickness of biosphere, which is still only about 0.3 % of earth's radius. Cockell stated, "Life is denied depth of earth bc of thermal energy", and "Between absolute zero and the temperature of interior of a star like the sun, life occupies only 0.007% of this temp range."
Does Cockell or anyone understand all the equations of life? Of course not. But this is certainly a good place to start.
There was quite a bit of discussion about the origin of life: how could lipids initially form into membranes; the tendency for molecules to want to disperse and not gather together to make the energy cells need; how could a cellular bag trap enough energy to allow for repair and replication; is there enough energy in a warm little pond, ocean waves, or crashing meteorites to allow replication; etc. When it came to the origin of life section in the book, I felt like he could have been a bit more forceful with his arguments here. He was on the money, spewing out essential facts that *must* be considered in order to come up with an accurate theory of first life, but seemed to be afraid to say, "If your hypothesis cannot account for the energetics involved in first life, your hypothesis probably isn't a good one." The reason I think it was important for him to be a bit stronger with this section is that, his focus on biological theories agreeing with, and being constrained by, the laws of physics is what is new about this book. Much of the material about cells has been known for quite some time. The exquisite, yet older, detail laid out in this book is only necessary to include because it provides foundational information for his central argument, which is that biology is constrained by physics. Without making a strong argument against theories that do not take the second law of thermodynamics and other laws of physics into account, this book could be a summary of what is already known and well told in many other books. I am not saying Cockell doesn't get around to the point, but he often discusses theories that are not constrained by the laws of physics as viable theories, only to passively - and at a later point - describe the physics that these theories ignore. I think a reader who is not familiar with both physics and biology might be forgiven for missing the point at times. Another thing missing from his first life discussion was the evolution of channels. This is absolutely an essential point. If he argues throughout the book that there are some universal rules, and the most important among them are that any species must take in nutrients and expel waste products during metabolism, then they need channels capable of doing that. The person working tirelessly on that is Nick Lane. So again, I don't know why he would not specifically mention Lane's work here. I felt as if there were politics at play and I get so bothered when the politics of science get int he way of the science.
Despite the forgoing criticisms, which is actually more of a suggestion for his future writing than it is an actual criticism, this book is a solid 5 star book. In fact, if there was a 6 star option that could only be used once for every 75 books reviewed, this book would get that extra star.
Cockell did take a bold stand on what life could look like if found in different places in our universe. This whole discussion was spot on. You need a cellular bag, or a bag or some sort, to trap energy. That is thermodynamics 101. Anything without this enclosure (and channels) would dissipate its energy too quickly to evolve into any form. (See Jeremy England's work for more on that).
What are the equations that constrain the size of cells? (Nick Lane does really nice work on this. I cannot remember if it was in his books or talks- or both). A cell cannot get too large because it needs enough surface area to ingest nutrients. If the cell has a huge, greedy inside, then its membrane does not provide enough surface area to include the channels it would need to take in nutrients to satisfy the activities inside the large cell. The largest cells have a few tricks up their sleeves. A large cell could, like a parasite, live inside an animal, so that the animal does the work the cell would otherwise have to do. A large cell could also have invaginations, which allow the cell to pull in nutrients from the outside without having to provide more channels. This part of the book reminded me a lot of animal size discussed in Geoffrey West's book Scale. Even those animals who are allowed to grow to enormous sizes, because they live in water and gravity will not crush their organs and bones like it would on land, can only grow so large. Whales have only one heart. The arteries, veins, and capillaries are fractals. They branch and then repeat the same branching pattern from the very large blood passageways to the tiniest passage ways. Blood must be fed to each part of the tissue. But the blood passageway system can only stretch so far. If the animal is larger than the system can provide blood to the tissues, the tissues will die. Thus, blood supply constrains the size of all animals.
When discussing convergent evolution, I can't remember if Cockell even used the word homologous, but I don't think he did. He didn't need to because his entire focus was on how the small set of physical laws that govern the larger universe and our small world could of course dictate the shape forms can take, whether or not they are related. I hope that all classrooms in the near future teach convergent evolution through this lens.
If you like biochem, you will love Cockell's discussion of why, if we find life on other planets, it will likely be made of carbon. Each of the CHNOPS elements (carbon, hydrogen, nitrogen, phosphorus, sulfur) get detailed treatment in this book. To make any life, either on Earth or another planet, bonds need to form and break to build and evolve life forms. If bonds are too strong, such as the case with fluorine and carbon, and to a lesser extent, chlorine and carbon, then those bonds will not break as easily. If the bonds are not strong enough, as is the case with silicone based life instead of carbon life, then bonds break too easily and life can't hold together. The bonds have to be just right for the dynamic nature of life to play out.
If you doubt that the process of synthesizing biology and physics is new, take note of Chapter 11, in which Cockell highlights many of the challenges biologists and physicists face when they try to apply universal laws that could explain the physical and biological world we see around us. This is a subject that I have been writing extensively about, in a personal project, for the past 10 years.
The take home message is a reiterated in the last chapter when Cockell talked about the role of chance in evolution. Like Steven Jay Gould, Cockell is fascinated with the diversity of evolutionary forms. Even within the same form, like Gould's Burgess Shale, you can find immense diversity because of the emergence of various traits, which have either been selected for or selected against by the conditions in the environment. These variations are impressive to be sure. They even speak the role of chance. However, what is even more glaring is that within species and *across species*, there are shockingly similar rules that govern the shape and function of life. Every form, no matter if that form is a single cell, the Burgess Shale, a fish, a plant, a huge whale, or a human, *all* of these forms must have cells that contain enough surface area to take in nutrients and expel waste products. They must have an enclosed skin or membrane that helps them achieve this. For forms that grow large, they must have many cells, and many organs made up of cells that do the job of providing enough surface area to take in various waste products and expel waste. Take your own body. You must have cells and organs that take in oxygen. Your mouth does this. Oxygen is then taken in by your lungs and and is sent around to your organs via pumping of your heat (which itself houses cells that take in and expel the oxygen). Your mouth takes in food and breaks it down to harvest the glucose. That glucose is broken down even further to make all the energy you will ever need to carry out every single thought and action you will ever think or do in your lifetime. Glucose is also broken down to make CO2 that will be ingested by plants as their nutrients. They will expel oxygen as their waste product.
Not a single evolved form can escape the process of ingesting nutrients and expelling waste products. A system/ species that cannot do that is a system that cannot remain active and will die. So no matter what elements other planets might use to evolve life, that life will make enclosed membranes/skins that can take in nutrients and expel waste products. Physics mandates this. There a small set of rules that confine what life can look like. Cockell boldly stated that what once seemed limitless and overly complex (the process of evolution) is now more simplified because of the convergence of biology and physics. In my opinion, there is notting more important problem/field that a scientist could be working on. I highly recommend this book.