The topic of evolution and mass extinctions is an interesting one, and I liked how Michael Tennesen provided such a great amount of information in such an engaging manner. I enjoyed the book thoroughly, and it is a read that I highly recommend to those interested in learning more about scientific background and speculation surrounding the topic. It is amazing to see how some scientific speculation almost mirrors science fiction nowadays.

I obtained an advanced copy through Goodreads in exchange for an honest review. ( )

Although many parts of this book were interesting, it seemed to lack clear focus and organization. I was also bothered by his often uncritical acceptance of what are, at best, unsupported speculation, especially on topics like the origin of life on earth and elsewhere in the universe. His speculations on the possibility of humans colonizing Mars were also misleading to some extent. He seemed to gloss over the biggest challenge, the extremely thin atmosphere on Mars, that would essentially require space suits for all outdoor excursions. He also makes no mention of the dangers of cosmic rays to any expedition traveling to Mars. Lastly, his discussion of uploading human minds into computers and his discussion of AI were both too cursory and too unrealistic. And interesting read, but I have read better books on these topics. ( )

A multi-angled, reportorial build-up to the case that a largely human-caused mass extinction is not far off and that _H sapiens_ itself may be among the extinguished species. (It's funny how *both* future-doom books like this one and future-wonder ones like Kurzweil's seem so convincing at the time you read them.) Tenneson likens humankind to a virus, whereas I've always thought that the right metaphor is that of a cancer. In either case, its departure will be a great benefit to the rest of Earth's biosphere.

Waiting for the Sixth Mass Extinction – or something like it

The high points, if that is the term, of The Next Species demonstrate how tampering with one species or ecological unit like a forest can wreak unintended havoc far and wide. The removal of a top predator can result in the denuding of forests, as leaf eating prey are suddenly free to overrun the area, stripping it bare. This permits other plants, formerly hidden and controlled, to take over, and even prevent trees returning. Whole forests are disappearing “naturally,” thanks to the hunting, urbanization and pollution by Man. It’s one of many eye-openers in this important overview of the state of the disaster.

One more: an unexpected chain reaction is occurring in the oceans of the world. The slaughter of great whales from the millions to a few thousand has led to killer whales being forced to hunt otters instead, which lead to the overabundance of sea urchins that otters ate. The urchins kill off the kelp forests underseas, and that removes the whole ecosystem where fish bred. The result is massive dead zones where life once teemed.

Agriculture has become its own plague, as farmers sterilize the soil, dry it to dust, drain pesticides and fertilizers into the watershed, destroy habitats with single crop policies and expose vast areas to damage from weather, such as erosion, and draining and drying of aquifers.

Even good intentioned efforts to release animals into the wild are misguided and doomed to fail, as one additional life form does not imply a return to homeostasis. They can and do create other problems when they don’t simply fail.

Unlike the previous five mass extinctions due to volcanic eruptions and meteor hits, this one is happening in slow motion, as Man eliminates one species after another, by hunting, by poisoning and by habitat elimination. Biodiversity is already down almost a third just in our lifetime, and diversity is what keeps disease in check, as well as improving genetic advantages. The remaining life is subject to worsening health and a degradation of the environment it can no longer keep going, a downward spiral.

Sadly, the clear takeaway is that the removal of just one species will allow the Earth to rebalance and replenish, and function for the good of all. “In many ways, we’re the worst of the invasives,” Tennesen says.

There are all kinds of indications that new top species evolve to take over. The rise of Humboldt squid is a fascinating case study Tennesen uses to demonstrate how voids get filled and whole ecological systems change.

After we have totally trashed Earth, we will want to start over. Tennesen examines Mars, and it seems numerous projects are already underway. The most classic manmade solution is a Dutch project to produce a TV reality show there, the whole thing financed by the broadcast rights. Despite it being a one way trip, more than 100,000 people have signed up. Mars will never be the same. (See Earth.)

Unfortunately, life on Mars will change homo sapiens into something else, as the weaker gravity will change our bodies (so that we can never return), and the sterile environments we must create will cause us to mutate, weaken and stagnate. If we stay on Earth until we destroy it, we will adapt to fit the new reality, and again, it will be different and decidedly not better.

This is not a cheerful picture. It is at once fascinating and horrifying. To paraphrase David Suzuki, we are in a car racing over a cliff while arguing over who gets to sit in the front seat. We can only hope that whatever comes after us proves somewhat more benign. ( )