Tag Archives: Biology

Brain Size Is Not A Filter

We relate brain size to appearance time for 511 fossil and extant mammalian species to test for temporal changes in relative brain size over time. We show that there is wide variation across groups in encephalization slopes across groups and that encephalization is not universal in mammals. … Encephalization [vs. time] trends are associated with sociality in extant species. These findings … highlight the role sociality may play in driving the evolution of large brains. (more; HT Razib Khan)

The biggest brains have consistently gotten bigger over the last half billion years since multi-cellular life appeared. Big brains seem to be a necessary precondition for human level intelligence and civilization, and human size brains appeared only very recently. These facts strongly suggest that achieving human level intelligence is just not a big component of the great filter.  It appeared quickly after big brains, and big brains seem likely given enough time and sociality, and sociality seems likely.

This unfortunately means that it is very difficult to collect data on all steps of the great filter.  It is big and real and matters enormously, but we can hardly see it.

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Green Is Far, Mostly Pink

I’m teaching environmental econ again for the first time in six years, and reviewing some standard texts two things stand out:

  1. Green Is Mostly Pink – Weighted by public or private efforts, most environmental policies are focused on limiting the harm some “pink” humans do to others via intermediaries of air, water, food, light, or sound. Whether that harm passes through green stuff is incidental to such policies. Much of the rest focuses on vague concerns that current human ways are not “sustainable.” What little concern there is about green stuff out there is mostly to ensure humans have nice green places to visit when they want, and that humans avoid guilt for stuff that happens out there due to their intervention. Actually concern for the welfare of green stuff from its own point of view is pretty minimal.
  2. Green Is Far – At first, I found it hard to see what the various “environmental” topics have in common. Air purity, food locality, future human population, animal experiments, oil & mineral depletion, energy efficiency, sea levels, urban sprawl, landfills, consumerism, – what unites such diverse topics? And then it hit me: they are mostly rather “far“. That is, “environmental” concerns tend to be at unusually large distances in space, time, and social relation from ordinary folks and concerns. The common theme seems to be how we here now relate to much larger contexts, and the oddities of far-mode thinking go a long way to explain odd enviro thoughts.  Cosmology would be super-green, if folks thought we had a non-trivial relation to non-Earth life.
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More Diversity Or Less?

Nature reviews Biology’s First Law: The Tendency for Diversity and Complexity to Increase in Evolutionary Systems:

McShea and Brandon state that diversity and complexity tend to increase over time in biological systems. It is, the authors argue, a universal law, applicable to all taxa, at all hierarchical levels and at all times. They use the analogy of Newton’s law of inertia — just as it tells us that a body will move with a constant velocity if no forces act on it, this zero-force evolutionary law seeks to capture how a biological system will behave in the absence of other influences. Although the trend they describe may not manifest itself in cases when it is counteracted by constraints, it provides the background against which other evolutionary pressures should be understood.

The authors adopt a simplified measure of complexity that considers only the degree of differentiation among the parts of a biological system, not the various functions of those parts. … The authors argue persuasively that their simpler definition of complexity is more scientifically useful … because function is hard to quantify. … Diversity at one level of the hierarchy equates to complexity one level higher. Both diversity and complexity will increase over time through the accumulation of mutations, they suggest. …

The tendency for increasing diversity has been recognized previously in specific situations. … The authors aim to encompass these various findings in a single theory that covers all of the fields in which the principle has been seen. … They make a good case for their argument that a single principle is at work. …

Their theory suggests new research questions, such as whether the tendency for diversity to increase will usually be overcome by natural selection, and it advances our philosophical understanding of evolution. The law also makes testable predictions: for example, that diversity and complexity will increase fastest in ecological circumstances and taxa where selection is weak.

This is a deliciously vast topic, with huge long term implications. Overall, diversity has clearly increased within biology on average over time. Very recently, humans have displaced other biology diversity with human diversity. Within the human realm, many kinds of diversity have also increased, though some kinds have decreased as well. The big open question: will diversity continue to increase, or at least not greatly decrease, into the distant future?

One the one hand you might think that physics is the same everywhere, matter doesn’t vary that much, and there is only one very best way to arrange atoms for any particular purpose. So within a million years we’ll figure out the most competitive local designs and from then on everyone will use them.  Surely there is a lot of truth in this.

On the other hand, the very best design for any one thing may depend greatly on other choices made nearby, and ancient legacies, choices made long ago that are too expensive to change, may vary greatly from place to place. And there should be far far more places out there, only weakly connected to each other due to vast distances and light-speed limits.

On a third hand (oh someone will have them), the future might not be competitive, if a stable world government arises before our descendants radiate rapidly out into the cosmos, and if there are no aliens that matter out there. Such a stable central power might work to reduce diversity, to cement its hold on power. (More on world govt here, here, and here.) Or perhaps it will have stable preferences, unchallengeable power, and prefer to create diversity.

So, will diversity increase in the long run?

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Ancient Hobbits

It remains one of the greatest human fossil discoveries of all time. The bones of a race of tiny primitive people, who used stone tools to hunt pony-sized elephants and battle huge Komodo dragons, were discovered on the Indonesian island of Flores in 2004. …

According to a growing number of scientists, Homo floresiensis is probably a direct descendant of some of the first apemen to evolve on the African savannah three million years ago. …  It sounds improbable but the basic physical similarity between the two species is striking. … Analysis of Lucy’s skeleton shows it has great similarities with the bones of H. floresiensis, although her species died out millions of years ago while the hobbits hung on in Flores until about 17,000 years ago. …

The crucial point about this interpretation is that it explains why the Flores people had such minuscule proportions. … In research that provides further support for this idea, scientists have recently dated some stone tools on Flores as being around 1.1 million years old, far older than had been previously supposed. … He has now uncovered stone tools on nearby Sulawesi. These could be almost two million years old.

More here.  HT Tyler.

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Animal Smoking Studies

Some seem to think experiments show smoking causes cancer in animals.  Not so, for mice or rats:

I review the results of a representative selection of chronic inhalation studies with rats and mice exposed to mainstream cigarette smoke. … Smoke-induced epithelial hypertrophy, hyperplasia, and squamous metaplasia were reported in the conducting airways in most of the studies, along with increased numbers of intra-alveolar macrophages that were occasionally associated with alveolar metaplasia. Lung adenomas and adenocarcinomas were reported in only a few of the studies. No statistically significant increase in the incidence of malignant lung tumors was seen. …

The 14 studies reviewed … [showed] significant increases in the numbers of malignant tumors were not produced in the respiratory tracts of rats or mice exposed chronically by inhalation to cigarette smoke.  The studies clearly involved the inhalation of very large amounts of smoke (usually from unfiltered, high-tar cigarettes) …  The results of this work clearly indicate that maximal amounts of smoke were inhaled into the lungs of the animals (blood COHb concentrations very close to those associated with lethality) daily for up to 2 yr with no carcinogenic effect noted.

Nor for hamsters, dogs, or primates:

This paper makes an identical evaluation as before, but, restricting the species being evaluated to representative studies of smoke-exposed hamsters, dogs (both by tracheostomy and by direct inhalation), and nonhuman primates. As was seen previously, no statistically significant increase in the incidence of malignant tumors of the respiratory tract was found in any of the 3 species, even though very long exposures and high doses of smoke were used.

Now the number of animals in these studies is a few thousand at most, and their duration is less than decades, but experimenters did have complete control over making animals smoke heavily.  Yes this review author works for a tobacco firm, but his papers seem professional.

Searching for “animal smoking experiments,” I found many sources admitting we haven’t found much evidence smoking hurts animals, and none saying the opposite.  Here is a ’97 Scientific American article “Animal Research is Wasteful and Misleading”: Continue reading "Animal Smoking Studies" »

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Monogamy Is Human

It easier to maintain pair bonding in larger primate social groups if males can’t easily tell when females are fertile.  In turn, monogamy makes it easier to keep the peace in larger groups.  And since folks in large groups have more uses for big brains, and more resources to pay for them, monogamous social apes should have bigger brains.  So monogamy encouraged by hidden female fertility may have been the key to humans succeeding far beyond other apes.

Why might we think this?  Chimps are humans’ closest living relatives, splitting apart 5-7 million years ago.  The Ardipithecus ramidus proto-humans of 4.4 million years ago were bipeds with a broad diet in woods and grasslands, and with a brain

about the same size as a modern bonobo or female common chimpanzee brain … The less pronounced nature of [their] upper canine teeth … has been used to suggest that the last common ancestor of homonids and African apes was characterized by relatively little aggression between males and between groups.

A recent Science article persuasively elaborated this argument:

Elimination of the [upper canine teeth] in hominids is unique among all higher primates and occurred long before Australopithecus. … Available evidence now suggests [it] was, as is theoretically most likely, a social adaptation … consistent with a strategy of increasingly targeted provisioning. …. Males would benefit from enhanced male-to-male cooperation …. Foraging could be achieved most productively by cooperative male patrols … Provisioning would reduce female-to-female competition … and would improve (or maintain) social cohesion. …

A large brain is not our most unique characteristic. … The combination of [upper canine teeth] elimination, habitual bipedality, and reproductive crypsis (each in itself an extreme rarity) is unique among all known mammals. Conversely, simple brain enlargement is readily explicable in myriad ways.

They plausibly suggest that these three key uniquely human features appeared together over 4 million years ago, leading over time to our uniquely large human social groups and brains, and all else they imply.

If monogamy is this essential to human success, that does make me a bit more concerned about current trends away from monogamy.  Of course hunter-gatherer monogamy may only have been for 4+ year periods, and we are in some ways moving more toward that.  But still, it gives me pause.

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Humans Are Evolving

The team studied 2238 women who had passed menopause and so completed their reproductive lives. For this group, Stearns’s team tested whether a woman’s height, weight, blood pressure, cholesterol or other traits correlated with the number of children she had borne. They controlled for changes due to social and cultural factors to calculate how strongly natural selection is shaping these traits.

Quite a lot, it turns out. Shorter, heavier women tended to have more children, on average, than taller, lighter ones. Women with lower blood pressure and lower cholesterol levels likewise reared more children, and – not surprisingly – so did women who had their first child at a younger age or who entered menopause later. Strikingly, these traits were passed on to their daughters, who in turn also had more children.

If these trends continue for 10 generations, Stearns calculates, the average woman in 2409 will be 2 centimetres shorter and 1 kilogram heavier than she is today. She will bear her first child about 5 months earlier and enter menopause 10 months later.

More here. And this is just for the few parameters tested in this study; no doubt many more features are evolving as well.

Our culture respects taller thinner women who wait longer before having kids, but in fact we are evolving short heavy women who have kids earlier.  Shades of Idiocracy – in many ways we are evolving to become less of what we now respect.

In principle humans could implement strong central regulations to ensure that they evolved to become the sort of creatures they respect, at least regarding a few features of regulatory focus.  But it is far from clear that we are willing, or even able, to achieve this.  And it is far from clear to me that we would be better off achieving such far ideals. Perhaps short plump early moms are happier, after all.

Of course I expect that within a century the main dynamic will be even faster robot evolution, but the same principle will apply – without strong central coordination they are unlikely to evolve to become what we or they most respect.

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Bad News On Human Extinction

Disasters that destroy all but a thousand humans are more likely than disasters that destroy all but a hundred humans.  So this news says human extinction is more likely than we thought:

Conservation biologists may be deluding themselves. An analysis of the minimum number of individuals needed for a species to survive in the long term has found that current conservation practices underestimate the risk of extinction by not fully allowing for the dangers posed by the loss of genetic diversity. If correct, it means the number of individuals in endangered species are being allowed to dwindle too far.

Lochran Traill at the University of Adelaide, Australia, and colleagues found that for thousands of species the minimum viable population size (MVP) – where a species has a 90 per cent chance of surviving the next 100 years – comes in at thousands rather than hundreds of individuals. Many biologists, Traill says, work with lower numbers and so allow unacceptably high extinction risks.

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Height Puzzle

Among adults of industrial nations, growth stunting … is associated with worse indicators of adult well-being (e.g., income). … Here we … [consider] the Tsimane’, a foraging-farming society of native Amazonians in Bolivia. Subjects included 248 women and 255 men measured annually during five consecutive years (2002-2006). Nine outcomes (wealth, monetary income, illness, access to credit, mirth, schooling, math skills, plant knowledge, forest clearance) were regressed separately against a stunting dummy variable and a wide range of control variables. We found no significant association between any of the indicators of own well-being and adult stunting. …

In South Africa, a comparison of short-for-age “Cape Coloured” children showed that those growing up under poorer socioeconomic conditions had lower body weight, height, and physical performance than the more advantaged children … Among adults of industrial nations, standing physical stature is positively associated with many indicators of own adult well-being, such as occupation, monetary income, wages, IQ, longevity, and good health.

More here.

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Nature is Doomed

Long ago humans pioneered some very powerful innovations, innovations that have allowed us to grow in capability much faster than the rest of nature.  As humans grew more capable, we learned to live in more kinds of places, and to use more of the plants and animals in each place.  We didn’t always destroy non-human living nature – sometimes we converted it to farms, pets, or parks.  But we only left nature alone when we couldn’t figure out how to make use of it, or of what it used.  Our expanded use of nature has left less for other species, often leading to their extinction.

This trend has continued in recent times: as we learn more ways to use nature, we use nature more.  There has been, however, one notable exception: rising wages over the last few hundred years have made us abandon some old practices.  For example, during the depression my grandparents farmed marginal land in Kentucky that is now forest.  We still know how to farm the land, and with free immigration it would still be farmed, but as it is labor is too expensive for farming.

This reprieve won’t last.  Wages have risen because economic growth rates have outpaced feasible rates of growing well-trained people.  But current growth rates simply cannot continue at familiar levels for ten thousand more years.  We’ll eventually learn everything worth knowing about how to arrange atoms, and growth in available atoms will be limited by the speed of light.  So over this timescale growth rates simply must fall below feasible population growth rates.  (I actually expect a new brain emulation tech to allow very fast population growth in a century or two, but this is tangential to my argument here.)

With familiar competitive habits, this growth rate change implies falling wages for intelligent labor, canceling nature’s recent high-wage reprieve.  So if we continue to use all the nature our abilities allow, abilities growing much faster than nature’s abilities to resist us, within ten thousand years at most (and more likely a few centuries) we’ll use pretty much all of nature, with only farms, pets and (economically) small parks remaining.  If we keep growing competitively, nature is doomed.

Of course we’ll still need some functioning ecosystems to support farming a while longer, until we learn how to make food without farms, or bodies using simpler fuels.  Hopefully we’ll assimilate most innovations worth digging out of nature, and deep underground single cell life will probably last the longest.  But these may be cold comfort to most nature lovers.

Yes, nature would be saved if we destroy ourselves without destroying nature in the process, but hopefully we’ll avoid this scenario.  We might also somehow coordinate to prevent competitive growth.  For example, we might empower a world government to protect nature, prevent innovation, or prevent population growth.  But I honestly see little prospect of this.  We now live in a very competitive world, and even governments mainly just redirect competition, toward controlling those governments.

We like nature, but aren’t really willing to pay the price it would take to save most of it.  Nature than cannot survive as farms, pets, or small parks, is doomed.

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