SHORT SUMMARIES

Tim White explores the question “where do we come from?” by guiding us through recent discoveries in human evolution. Given the evidence about human origins that we have amassed since Darwin’s time, he asks how we might better educate the public about the knowledge we have acquired, so that people will better understand their proper place in the natural world.

Tony Barnosky examines whether we are now living in the Anthropocene, a new geological epoch in which humans are exerting an unparalleled influence on the earth’s ecosystems and atmosphere. Comparing recent ecological changes with those that marked the shift from the Pleistocene to the Holocene, he argues that there is substantial evidence that we are indeed living in the Anthropocene, and considers what this implies about our future on Earth.

Jeff Boore explains that an answer to one of the questions about what makes us human is found in genomic research, where it turns out that only a small amount of genomic difference accounts for all of the significant differences between us and chimpanzees. In light of this fact, he raises a series of questions regarding how we understand the human relationship to the environment.

Tom Carlson considers human impact on the environment, and argues that it is important to examine the differential impacts of diverse groups. He highlights two such examples: the local case of how wolves are treated in Siskiyou County, and the global case of ultra-consumer vs. low-consumer carbon footprints. He argues that among our approaches to addressing climate change we should look to these low-consuming communities and see how they get along with a minimal carbon footprint, thus employing not only new green technologies, but ancient technologies as well.

Paul Rabinow emphasizes that we need a different conceptual repertoire for coping with the future. This involves rethinking the university and how we treat the production of knowledge. He illustrates his points by exploring a few examples from his work in molecular and synthetic biology.

Richard Norgaard points out that most of us don’t really live in the natural world. Rather, we live in the “econosphere.” While population has increased by 4 or 5 fold during the 20th century, the world economy grew 50 fold. He contends that we need to recreate that economy to live in concert with nature.

LONG SUMMARIES

Tim White’s presentation explores the fundamental question: where do we come from? But of substantial importance is the related question: given all the evidence we have acquired about human origins, “why is it so difficult for 21st century people to comprehend their place in the natural world?”

Dr. White posits several answers to this latter question: 1) time is deep; 2) we are very peculiar among mammals; 3) the weight of evidence is not yet generally known; and 4) the weight of evidence is trumped by beliefs. In an attempt to counteract these opposing forces, Dr. White highlights some important evolutionary aspects of the hominid clade.

It can be difficult for humans to understand and appreciate the time that has preceded us, and this problem increases the further back in time we try to cast our attention. Although the ability to look forward in time is fitness enhancing, looking backward is relatively unhelpful, so we’re not as adept at this and lack many tools for tracking it accurately. When we come to contemplate geological time, it is difficult for us not only because of vast temporal distances, but also because of what it implies about our place in the world. Steven Jay Gould expressed this as “geology’s most frightening fact.” As Dr. White puts it: “If you recognize that humanity arose, metaphorically speaking, yesterday as a tiny twig on the branch of a flourishing tree, then it puts serious pressure on the idea that life exists for us or because of us.”

While there is a lineage that we can trace back to our closest common ancestor with the great apes, there were other lineages as well, though these have expired. How many? Human evolutionary history is often viewed as a “bush” with many branches, stemming from adaptive diversity and a multiplicity of lineages. But Dr. White says he’s going to “take some shears to the bush.” A recent book claims that there have been 22 different hominid lineages (plus four others that have been proposed since). However, Dr. White argues that the diversity of names does not equal the diversity of species lineages. There are many arbitrary “chronospecies.” For instance Homo rhodesiensis is widely agreed to be the direct forbearer of Homo sapiens (which emerged around 160 thousand years ago [ka]), but they are the same lineage. So the bush is the wrong botanical metaphor. It’s more like a Saguaro cactus. Over the last 5 million years (Ma) there has been some separation of a few different lineages, but at the most diverse point about 2 Ma, there are still only 4 of them: it’s not an adaptive radiation. So why is diversity so limited among hominids?

The answer is because “hominids were large terrestrial generalists with increasingly broad ecological niches; intelligence and culture increased niche breadth, and reduced opportunities for sympatry.”

What happened over the last 1 Ma to the hominids that dispersed from Africa around 2 Ma? Humans underwent dramatic change, unlike for instance, hyenas over the same time period. Why? Some Environmental Determinists suggest that this happened because of glacial pulses over time. But these pulses also affected the hyena, so this isn’t a very compelling explanation. The important point is that hominids are culture-bearing. Culture, and special technology, has driven a lot of this dramatic evolution, allowing also wide geographic expansion. White illustrates our increasing knowledge of hominid ancestry with reference to Ardipithecus, one of the earliest relatives that we share with the great apes.

So the question is, given the increasing evidence about our evolutionary history, how can we make it the story that people understand and accept? As Dr. White puts it “our task is education, our tools are evidence and reason, and our goal ought to be sustainability. That is really the big picture of human evolution.”

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Tony Barnosky’s presentation asks whether we’ve moved into a new geological epoch. Are we no longer living in the Holocene, but rather, the Anthropocene, a time where humans are exerting unparalleled influence on the earth’s biosphere, atmosphere, and geosphere?

Earth history can be divided into small subdivisions termed epochs. Within an epoch, the earth remains in a certain state that includes certain characteristic taxa, interactions among them, ecosystem structures, etc. Across the boundaries between epochs, things change, “suddenly” in geological time (that is over tens or even hundreds of thousands of years). 

Is the Anthropcene a real epoch, or is it just a way of making ourselves seem more important than we are? Dr. Barnosky suggests that the test is to examine whether the changes we’ve seen taking place (mostly in our lifetimes) are greater than those that took place across the last epochal boundary from the Pleistocene to the Holocene.

Dr. Barnosky explains that if we go back to that last transition (around 11.7 ka), there were some big changes occurring. It was around that time that humans become distributed almost worldwide. This was also the transition from the last ice age into the present interglacial period (global temperature increased around 5˚ C). So if we compare the changes happening now to the ones happing then, what do we see?

Dr. Barnosky compares these two transitions across four dimensions.

1) Human population growth.—The balance of power among species began to shift around 11k years ago. Earlier (back to around 100 ka) there were around 350 megafaunal taxa, mammals whose average bodyweight is over 100 lbs. Human population growth blossoms around the Pleistocene to Holocene transition, and correlates with a crash in the number of other megafauna. So most of the “ecological energy” (so to speak) began being routed through humans as opposed to being distributed among other animals. Megafaunal biomass in general crashes at this point, but then builds back up in the form of humans and domesticated animals. But once we hit the industrial revolution, this number shoots up dramatically, far beyond the carrying capacity of the earth for organisms of this kind. How does that work? Dr. Barnosky explains that we began digging for fossil fuels and inputting this energy into a global ecosystem based previously on sunlight and photosynthesis. However, our reserves of fossil fuels are now dwindling. Thus, we need new energy sources as soon as possible if we’re even going to have enough energy available to sustain something like the present population.

2) Global climate disruption.—Between the Pleistocene and the Holocene there was a temperature increase of about 5˚ C. According to the Intergovernmental Panel on Climate Change (IPCC), no matter whether it’s the best or the worst outcome, 2050 will likely be the warmest climate Homo sapiens has ever experienced. If we stay on the current path, the earth will be the warmest it’s been in 14 million years. In the worst-case scenario, we’ll be back to Eocene temperatures when there were topical and subtropical forests growing in Wyoming.

3) Habitat fragmentation.—From the Pleistocene and the Holocene, the surface of the earth changed dramatically with glaciers coming and going. Fires and other natural phenomena also contributed to changing landscapes. In comparison, think about the present day. In the US, you are on average less than 3 miles from a road no matter where you are; and of course in most places, its much more dense than that. So we, too, have cut-up the landscape considerably.

4) Planetary feedbacks.—At the Pleistocene-Holocene transition, the ice melted back and revealed darker vegetations and soils which absorbed heat and created a feedback loop: these local changes had global effects, which Dr. Barnosky calls “Sledgehammer Effects.” A modern Sledgehammer Effect stems from clearing an agricultural field, which has effects on adjacent areas that are not altered directly. And these changes accumulate. About 40% of the land-surface has now been converted to farms and ranches. If you change that much of the world, you have larger scale effects. For instance, nitrogen dumped on farms runs down the Mississippi, increases nutrient loads in the Gulf of Mexico, algae blooms, sucks the oxygen out of the water, and everything dies. Other effects stem from the burning of fossil fuels, and from climate change.

So are we in the Anthropocene? Dr. Barnosky says: “My answer to that is yeah, no doubt about it.” We have changed the planet more since 1950 than we saw across the last glacial-interglacial transition. There is some controversy about whether the Anthropocene began around 1800 (at the time of the industrial revolution), or closer to 1950 (at the time of the human population boom and the most dramatic ecological changes), but according to Dr. Barnosky, the idea that we are living in the Anthropocene is really not in doubt.

In this light, Dr. Barnosky asks us to consider the future. Ecologists often think of progressions of changes and threshold events (dramatic changes where we flip into a new state). For example, if you clear cut 50% of the forest, you begin to see tipping point state-changes in the undisturbed patches. Now if you think about the global scale of agricultural development, (recall that we have already developed 40% of arable land) we’re getting pretty close to that point. Each individual of the 7 billion people on Earth requires 2¼ acres to be sustained in order to continue in the manner that we’ve become accustomed to. At that rate, by 2045, we’d require 60% of the earth as agricultural land, which would likely cause large-scale change across the entire planet even beyond what we’re directly disturbing.

Dr. Barnosky says: “As scientists, I think that we can look into the future; and I think we still have a more or less healthy planet that we can guide. But it takes getting the word out and making people aware of what the realities really are.”