I've been reading this 2024 book by Daniel R. Brooks and Salvatore J. Agosta. Because it covers themes that I've discussed on this blog many times, rather than provide a detailed discussion of the book, I'm only going to mention things that interest me now. In my readings, I've come to feel that field biologists such as Brooks and Agosta are the best qualified to write books concerning how we should think about our context as organisms on Earth. Frankly, at this point I'm quite tired of scientists who come up with cute mathematical formulas that describe biological events, and then go on to be lauded as the latest scientific geniuses; my feeling is that a full understanding of biological events is well beyond human cognition. This academic phenomenon, I think, is related to Sabine Hossenfelder's dislike of string theory in physics. Mathematics, while obviously a valuable tool in the sciences, has also become a shortcut to professional advancement in the field of biology. Underlying this phenomenon is the prestige that was conferred to physicists such as Albert Einstein. I prefer field biologists who write in the scientific tradition that dates from Charles Darwin and Alfred Russel Wallace and can be seen in varying degrees in writers such as E.O. Wilson, Jonathan Losos, Rachel Carson, Frans de Waal, Jane Goodall, Ian Tattersall, Robert Sapolsky and Nichola Raihani. What concerns me is that we seem to have entered the Anthropocene epoch, which entails not just climate change, but the potentially preventable deaths of billions of people, when little action is being taken by many modern governments. For example, the three branches of the U.S. federal government are currently led by people who are scientifically illiterate, several other countries are theocracies, and many of the remaining countries are led by oligarchs who take no interest in science that is unrelated to their continued control of their governments. I must also point out that, in a situation like this, democracy is hardly a panacea, because most voters are scientifically illiterate and are therefore likely to vote for scientifically illiterate candidates. Furthermore, in democracies, the most popular candidates are often the ones who promise the most to voters and diligently avoid the suggestion that voters may ever have to make sacrifices.
Parts of the book discuss the biosphere and ecosystems:
The biosphere is robust, responsive, and resilient. There are, however, limits to the evolvability of its species. Darwinian evolution produces prodigious amounts of potential to cope with change, but it cannot anticipate the future. Organisms might appear to do so, yet only in the sense that conservative inheritance provides a means of "predicting" that tomorrow will be mostly like yesterday and today. Day-to-day, this tends to be a sufficient strategy for survival. Most of the time tomorrow is like today, but periodically, this fails. As Darwin and Wallace recognized, extinction is a fundamental part of evolution....When the environment is stable, evolution is survival of the fit with the fittest dominating numerically. When the environment changes, evolution is survival of the fit with the fittest becoming less numerous or going extinct, replaced by variants that were less fit in the previous environment. If by chance no variant is fit enough to cope with the change, then despite whatever preexisting potential the system may have had, it will go extinct....The biosphere is dynamic and resilient. Its ecosystems will not fall apart if some species are lost. The robustness of ecosystems to perturbations increases as additional levels of complexity emerge, and high levels of complexity is a hallmark of the biosphere. That complexity is embodied in the diversification of species and the interactions they form with each other. The conservative nature of inheritance and capacities for ecological fitting ensure enormous amounts of potential within the biosphere at any time. If the loss of a few species or even the breakdown of some ecosystems could cause the entire biosphere to collapse, life on this planet would have disappeared long ago.
There is also discussion of mass extinctions:
Paleontologists have identified five episodes that they call the great mass extinctions. Narratives focusing on what was lost give the impression of a biosphere teetering dangerously close to the gambler's ruin. But in a Darwinian world, so long as some life survives, much evolutionary potential is preserved. The most recent mass extinction that wiped out the dinosaurs, for example, led not only to an explosion of mammal diversity including us but also the diversification of the few dinosaur species that survived into what we now call birds. By concentrating on the aftermath of the great mass extinction events, the potential for evolutionary renewal becomes apparent. Mass extinctions are mass evolutionary resets producing new diversity following close encounters with the gambler's ruin.
The evolution of the genus Homo is discussed. The genus is about 2.3 to 2.8 million years old. H. sapiens is about 300,000 years old. The authors describe the origin of H. sapiens in much the same way as the authors of other books I've read, but their description is slightly more nuanced. At first we lived at the edges of savannahs in Africa but also spent time in forests. Initially, the savannahs were extremely dangerous to humans because of the presence of large predators. Over thousands of years, the surviving humans developed bipedal gait, language, large brains, tool-making skills and a high level of cooperation. It sounds as if there may have been a few Homo species that have never been identified. It also seems that our understanding of the migrations out of Africa is probably incomplete. The movements and their timing outside of Africa are also unclear. The genetic data isn't always available, because genes don't preserve well in the hotter regions of Africa. We do know that our ancestors interbred with Neanderthals and Denisovans. But there is also a strong possibility that there were several other Homo species that have never been identified and are now extinct. We may never know all of the details of our evolutionary background, but it would appear that our ancestors gradually acquired slightly greater skills and were eventually more adaptive than the other Homo species. Before the last Ice Age, they were able to make a variety of tools and were able to make complex objects such as ocean-going rafts. When different groups of hunter-gatherers met, there initially were not hostilities, and trading and intermarrying began. Sometimes they would run into different Homo species. Jean-Jacques Rousseau was probably correct at least in the sense that at times in the past, when resources were readily available and populations were relatively low, there were fewer hostilities between different members of the Homo genus.
As far as I've read, I'm up to the Last Glacial Period, which started about 100,000 years ago, peaked about 20,000-25,000 years ago and ended about 11,500 years ago. During this period, all of the known Homo species except H. sapiens became extinct . We may be in the process of moving from an apocalyptic cold period to an apocalyptic hot period. I will continue reading and will have one or two more posts.