Life's Edge: The Search for What It Means to Be Alive in Science and Inquiry

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Life's Edge: The Search for What It Means to Be Alive

Carl Zimmer

Start date: September 1, 2021

Finish date: September 30, 2021

Discussion: Book Club 2021

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Book Club 2021

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What Members Thought

Mar 25, 2021 Petra lives on a little Caribbean island rated it it was amazing

Shelves: reviewed, 2021-read, medicine-science, 2021-100-reviews, review-at-last, 10-star-books

Before I read this book, I didn't think it was a problem defining what was alive and what wasn't. Now, I'm no more sure than the scientists and philosophers. If something dies after a 100 days, then it was alive, right? That's red blood cells. Not many of us would say they were alive, had life.

The most fascinating thing so far is a pretty, yellow single-celled slime mould (that isn't really a mould) that can grow all across a forest floor, can learn and can pass on its knowledge, although no on Before I read this book, I didn't think it was a problem defining what was alive and what wasn't. Now, I'm no more sure than the scientists and philosophers. If something dies after a 100 days, then it was alive, right? That's red blood cells. Not many of us would say they were alive, had life.

The most fascinating thing so far is a pretty, yellow single-celled slime mould (that isn't really a mould) that can grow all across a forest floor, can learn and can pass on its knowledge, although no one knows how. This is .

Physarum is chemically-attracted to various nutritive elements, say sugar. It is always hunting whether tiny in a laboratory or huge across a forest floor. It puts out tentacles which eventually will sense the sugar and move towards it. Where the tentacles have been is left a slime trail. Physarum will not go again where it has left slime, so it has 'memory' of where it has been. It also can only go where the surface is damp.

Scientists constructed an acrylic maze with sugar at the ends of it and damped the base. Over 120 hours, the slime mould had not just found the sugar but had done so in the straightest possible way. So, in another experiment (not in the book) scientists

"took 2,000 P. polycephalum specimens and trained them to cross a salt bridge to reach food. These were called 鈥渉abituated鈥� slime molds. Then, they took another 2,000 specimens and had them cross a bare bridge (no salt) to reach their food. They called these the 鈥渘aive鈥� slime molds. Then, they divided the specimens into habituated, naive, or mixed groups. The slime molds fused together when paired (a natural behavior). The researchers tested each fused group to see how quickly they would cross the salt bridge to reach food.

What they found was quite remarkable - any group that had contained a habituated specimen crossed the salt bridge just as fast as a habituated specimen alone! They went a step further and separated the fused specimens and found that only naive specimens that had been fused to habituated specimens crossed the salt bridge. The researchers take this as proof of learning. Now the trick is to figure out how the slime molds pass their learning to other individuals."

So now, it is not just life that has become hard to define, but also intelligence, communication and learning.

So, Carl Zimmer asks 'What is life?' and 'How did life begin?' The answer to the first is yet to be conclusively, scientifically defined, but we all know it when we see it. The answer to the second, only those who believe in creation stories know. The rest of us, that's an answer for the future. Maybe. ...more

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Jul 12, 2021 David Rubenstein rated it really liked it

Shelves: science, biology

"We cannot make artificial life because we cannot agree on what life is. We cannot find life on Mars because we cannot agree what life represents". --Radu Popa

Scientists still cannot agree on a definition of life. That is because life comes in so many forms and structures; there is no single definition that can encompass them all. That is the central theme of Carl Zimmer's book.

Zimmer's writing is excellent! He is a science columnist for the New York Times. He wrote a number of books. I really enjoyed his book She Has Her Mother's Laugh: The Powers, Perversions, and Potential of Heredity. I expect to read additional books he has written.

The early portion of his book discusses what is a human. When did humans first evolve? Zimmer writes a number of interesting anecdotes about primate behaviors and their reactions to death. One hundred-thousand years ago, homo sapiens began carrying out funerals. This demonstrates that people understood that diseases and injuries cause death.

Zimmer writes about flowers that were buried by Ice Age squirrels 30,000 years ago in Siberia. Scientists have nurtured them back into healthy plants. He writes about hibernating bats. He writes about Covid-19. Famous Hungarian biochemist Szent-Gy枚rgyi said that self-reproduction is not a requirement for life. As a humorous aside, he gave as an example that a single rabbit cannot reproduce.

The tail end of the book discusses the origin of life. Some scientists believe that the most important components or requirements for life are shell membranes called "liposomes". They act as containers for life's molecules. Scientists have made liposomes by adding water to meteorites. Other scientists find that visiting the Kamchatka Peninsula is a great place to study early-Earth-like conditions. The peninsula is packed with active volcanoes, crater lakes, hot springs and ponds.

This is just a small sample of all the topics discussed in this book. The author does not try to be humorous. Instead, he captivates the reader with an amazing assortment of stories about scientists who have tried to define the edge between the non-living and life. Highly recommended!

...more

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Sep 29, 2021 Jim rated it really liked it · review of another edition

Shelves: science, 2non-fiction, 1audio, historical

I was especially interested in reading this with the Science & Inquiry group since it's a question that's been on my mind since a dendrologist in a recent book said the bulk of tree wood was 'dead'. Others don't think so, but apparently we don't have a good definition for "life" or "death". I hoped that this book would shed some light on the subject. It didn't, but it was still an interesting trip through the history of our search for an answer & it was quite up to date.

The book started out slow ...more

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