Category: human evolution

ID craziness: Diarrhea and the appendix are signs of intelligent design

May 30, 2019 • 2:30 pm

It’s curious how adaptations that could have evolved by natural selection are nevertheless seen as evidence for Intelligent Design. Indeed, in the case of diarrhea and the appendix, as ID advocate David Klinghoffer maintains in the article below from Evolution News (click on screenshot), the evidence is not just an adaptation itself, evincing the wisdom of the creator, but supposed foresight: designing a feature in advance before it would be needed—something that natural selection couldn’t do. Unfortunately the article and associated video doesn’t show any such thing, nor does it show that ID is a more parsimonious explanation for diarrhea and the functionality of the appendix than is evolution.

Klinghoffer’s piece is about a recent book by Marcos Eberlin, a Brazilian chemist at the University of Campinas. (His Wikipedia entry states that “Eberlin is an advocate of intelligent design in Brazil, a pseudoscience on which he also lectures and he has signed the Dissent From Darwinism statement. He is a creationist also, and have said that evolution theory is a fallacy.”) 

So here are both Klinghoffer and Eberlin implying that that the Great Designer solves problems before they come up.  Klinghoffer’s blurb:

In his new book, Foresight, Dr. Eberlin develops a case for ID from the observation that so much in life and in nature appears to have been designed with a view to anticipating future problems and solving them ahead of time. Only minds can do that. Take the problem of eating adventurously and possibly consuming some bad food. The solution is diarrhea — the body’s “power wash” cycle, as he puts it. “It’s really nice,” he adds. “Diarrhea is a blessing.” You’ve probably never thought of it that way before.

But discomfort aside, the solution itself comes with a problem: it depletes the intestines of necessary microorganisms. The solution to that is the appendix, the supposedly useless, vestigial organ according to Darwinists, which in fact serves as a helpful reservoir of microorganisms.

And here’s Marcos Eberlin showing the creator’s marvelous foresight.

As for appendicitis, Eberlin claims that it’s only a problem in First World countries. I’m not sure if that’s true, and, if it is, why that’s so. Some hypothesize that in countries with less sanitation, the immune system gets used to challenges and there is thus less inflammation of this organ.  But the issue is whether the precursor to the appendix was, in net, deleterious in our ancestors, and, if so, that was the reason it shrank.

Let’s see if there’s good evidence for design here. First of all, diarrhea may well be a body’s way of flushing out toxic substances and microbes from the gut. There’s no problem with that evolving by natural selection, and this has been recognized by advocates of Darwinian medicine for a long time, as in the article below by Randolph Nesse (click on screenshot). I’m not sure that we know that diarrhea is an adaptation rather than an unevolved reaction of the gut, but at least there’s no barrier to seeing how a body’s expulsion of noxious substances could have been adaptive.

It’s also possible that the appendix serves as a reservoir of healthy gut bacteria to repopulate the intestine if it’s purged of its normal microbiome by something like diarrhea. This, too, has been suggested before, as in this paper in mbio six years ago. That paper proposes that “normal” gut bacteria are protected from purging by residing in a biofilm in the appendix, and then can reinvade the gut with healthy bacteria.

So it’s possible, and maybe even likely, that in general having an appendix is actually adaptive: you can repopulate your gut more easily with good bacteria if you have an appendix. And the “downside” of having an appendix—inflammation and death before it was possible to surgically remove it—may not have been something our ancestors faced often.

The question remains, however, whether the appendix is a vestigial organ—whether it is the remnant of a caecal pouch for digestion found in some of our relatives (some herbivores have pouches rather than an appendix). The important thing here is that vestigial organs can assume a new function. Despite that function, organs like the appendix could still be reduced remnants of a feature that once had a different (and useful) function, and thus, despite their new function, still serve as evidence for evolution. (There are, of course, many vestigial features that have no known function at all, like the muscles in human ears that can move them about or the “snake limbs” pictured below.)

It is one of the most common misconceptions about evolutionary morphology that to be vestigial, an organ cannot have a function. That’s not true: all that is required is that an organ be a reduced or degenerated remnant of a feature in an ancestor and have lost the function the presumably prompted its original evolution. It can still assume a new function.

One example: the reduced legs of snakes, which were once larger legs in their lizardlike ancestors. The males use these to stroke and stimulate the female during mating. They are clearly vestigial, as we know from both morphological and fossil evidence, but they still have a function.

Here’s a leg from the female of a ball python (Python regius), showing that the external leg is relatively short. (That’s a standard dissecting kit needle probe.) As Greg Mayer said, who provided the picture, “what you’re seeing is a claw; there’s a femur and pelvis inside.” This is clearly a vestigial feature, but it’s functional in males.

“… in snakes with vestigial limbs (e.g. Boidae), the pelvic spurs scratch or titillate the female in the vicinity of her vent.” —L. J. Vitt and J.P. Caldwell. 2009. Herpetology. 3rd ed. Elsevier, Amsterdam.

We’re not sure whether the appendix is a vestigial organ in the sense I gave above; the jury is still out. But what is absolutely clear is that there is no need to invoke the existence of a Wise Designer to explain both diarrhea and a bacteria-harboring appendix.

It’s entirely possible, for instance, that features of the gut causing diarrhea evolved as an adaptive response to toxins and bad microbes. Under many circumstances, the gut could repopulate itself from natural sources like food or contact with other individuals. But there might then be an additional advantage to those individuals who were able to sequester some of their gut bacteria on a wormlike structure of the gut: the appendix. That would be subsequent evolution by natural selection—no designer needed here, either. The whole sequence: appendix reduction—> evolution of diarrhea response—> co-option of the appendix to serve as a reservoir for “good microbiota”, can evolve by natural selection. And we don’t even need the first step should the human appendix prove not to be vestigial. Regardless of the sequence, no evolutionary “foresight” is needed.

We may not know whether the appendix evolved as a way to enhance microbe repopulation, or was the remnant of a caecal pouch that assumed this function as an adaptive byproduct. Some day we may have to revise our notion that the appendix is a vestigial organ, though I’m not ready to do that. But what is certain is that IDers like Eberlin and Klinghoffer are suffering from an extreme failure of the imagination in saying that diarrhea evinces an Intelligence On High, and that the appendix was put in place in advance to help those individuals who developed diarrhea.

 

h/t: Gregory

Human Phylogeography

February 23, 2019 • 11:33 am

by Greg Mayer

For the spring semester, my colleague Dave Rogers and I are teaching a seminar class entitled “Human Phylogeography.” Phylogeography is the study of the history of the genetic variation, and of genetic lineages, within a species (or closely related group of species), and in the seminar we are looking at the phylogeography of human populations. DNA sequencing now allows a fine scale mapping of the distribution of genetic variation within and among populations, and, remarkably, the ability to sequence ancient DNA from fossil remains (including Neanderthals). The seminar is based primarily on a close reading of David Reich’s (2018) Who We Are and How We Got Here (published by OUP in the UK).

A Krapina, Croatia, Neanderthal woman, photo by Jerry.

Although rarely under that rubric, human phylogeography has been a frequent topic of discussion here at WEIT, by Jerry, Matthew, and myself, including our several discussions of Neanderthals (or Neandertals) and Denisovans. So it may be of interest for WEIT readers to follow along. Below the fold I’ve placed the course syllabus, which includes the readings, and links to many newspaper articles of interest, and online postings, including many here at WEIT, and also from John Hawks Weblog, a site we’ve recommended on a number of occasions when discussing human evolution. (The newspaper links appear as images; just click to go to the story.) We just finished our third meeting, and I’ve been quite impressed by the students’ discussion and writing. We’re fortunate to have some students from anthropology or with some anthro background.

Please read along with us, or browse what seems interesting below. If you have questions or comments, post them here, and I’ll be looking in.

Continue reading “Human Phylogeography” →

Determinism doesn’t mean that you can’t change your behavior, or help others to

January 6, 2019 • 10:45 am

I’m a free-will “incompatibilist”: someone who sees the existence of physical determinism as dispelling the idea of contracausal, you-could-have-done-otherwise “free will”, which is the notion of free will most common among people. Many people find my view disturbing and fatalistic, and I’m often posed this question: “If everything is determined by the laws of physics mediated through our neurobiology, what’s the point of trying to change somebody’s mind?”

My response is that no, we can’t choose (via contracausal free will) whether we want to change someone’s mind, nor can they freely choose (in the same sense) whether to change it. But human brains are wired by both evolution and experience in a way that alters people’s behaviors when (in general) they would benefit from those changes. So, for example, if you learn that treating people in a certain way makes them treat you better back, your brain circuits for “better treatment” might be activated, and you might begin treating folks better.  And if you see someone treating others badly, your circuits to give them that advice might be activated. You might then advise them, and their own brain circuits may “take” that advice.

None of this is incompatible with determinism. People learn, often in a way that helps them get along better with others, perform better on the job or other aspects of life, and so on. The possibility of such changes might have been produced by evolution since such malleability might correlate with your status and well-being, which in turn might have been connected with your reproductive success. Or, on the cultural side, we avoid pain and seek pleasure, and our brains are capable of taking in advice or experience that would increase our well being and decrease ill being.

Likewise, advice from someone else can act as an environmental stimulus that activates brain circuits that alter behavior. Again, we have no free choice about whether to render advice to others, but that doesn’t mean that the advice can’t effect changes.

Pacific Standard has an interview with Stanford biologist and writer Robert Sapolsky, the author of the acclaimed book Behave: The Biology of Humans at Our Best and Worst. (Click on screenshot below for the interview.) Sapolsky discusses a lot of things about tribalism, but I’ll reproduce two exchanges about free will. (Sapolsky’s writing have shown him to be, like me, an incompatibilist who thinks that the notion of “you-can-do-otherwise” free will is an illusion.)

Here he expresses the difficulty in explaining to others why determinism doesn’t entail fatalism. Perhaps his answer is better or clearer than mine, and here it is:

TJ [Tom Jacobs]: You write that you don’t really believe in free will, but we nevertheless have an obligation to try to understand our behavior and make things better. Isn’t that something of a contradiction?

RS [Sapolsky]: I’m realizing how incredibly hard it is to articulate how an absence of free will is compatible with change.

Gaining new knowledge, having new experiences, being inspired by someone’s example—these are biological phenomena. They leave biological traces.

There are all sorts of neuro-pathways that analyze the world in terms of cause and effect. The knowledge that one person—or a bunch of high school students—really can make a difference can be inspiring. That means certain pathways have been facilitated, and, as a result of that, certain behaviors become more likely. Pathways to efficacy can also be weakened if you find out you have no control in a certain domain. Learning to be helpless is also biological.

TJ: So the fact free will is largely illusory does not mean the way we react to the world is static and unchanging.

RS: Absolutely not. There’s a vast difference between a biologically determined universe and fatalism.

h/t: Tom

Svante Pääbo gives a good public lecture on Neanderthals, Denisovans, and other relatives of modern humans

October 26, 2018 • 12:30 pm

I think most readers know about Svante Pääbo and his work on “paleoanthropology”: the study of the evolution and ancient movements of H. sapiens through analysis of “fossil DNA”.  His most famous work is on the genetics of Neanderthals, a subject in which I’ve recently become interested.

Pääbo’s work been extended to Denisovans and other previously unknown human groups, and what we’re learning is that even in H. sapiens the evolutionary tree is convoluted and interconnected. This does not, by the way, vindicate the thesis that evolutionary trees are wrong, or can’t be accurately determined. Despite that, there are some fossil individuals so genetically heterogeneous that they can’t be slotted into one group or another (see below). Our relatives were “mixing” quite promiscuously when they met.

In this remarkably clear lecture (h/t: Matthew Cobb), which proceeds chronologically through the scientific findings, Pääbo lays out the genetic data produced by his lab. (This is the award lecture accompanying Pääbo’s 2018 Nierenberg Award for Science in the Public Interest, given on October 3 of this year.)  There’s some freaky stuff in here, including an individual that appears to be an F1 (first-generation) hybrid between a Neanderthal and a Denisovan (about 32 minutes in).

36 minutes into the lecture, Pääbo summaries the contribution of Neanderthal and Denisovan genes to modern humans, including the possibility that a gene we carry from Neanderthals that now gives us a higher propensity for type 2 diabetes could have been an allele that helped Neanderthals deal with starvation. Similarly, Denisovans have bequeathed to modern Tibetan populations a gene that helps deal with high altitude.

In fact, there are at least a dozen “archaic” genes from Neanderthals and Denisovans that remain in our genomes and are associated with disease, perhaps because they don’t function well in the genetic backgrounds of modern humans. (There’s evidence that some of these have been selected against.) At the end, Pääbo discusses the genes in modern humans not present in Denisovans or Neanderthals; the idea here are that these human-specific genes (there are 87) that makes us “important” and “special”. I’ll let you watch those last 12 minutes on your own. There are four minutes of questions at the end.

All in all, this is a superb introduction to the complex and always-changing picture of our relationship to recent hominin relatives. If you watch it, and you should, you’ll be absolutely up to speed on human paleogenetics. But, as Steve Gould used to say, when he lectured on human evolution at Harvard each year, his first act was to throw out all his notes from the previous year’s lecture.

How do we know that Neanderthals were nearly all right-handed?

October 25, 2018 • 12:00 pm

A while back I wrote about my visit to the Croatia Natural History Museum, where curator Dr. Davorka Radovčić kindly gave three of us a several-hour look at Neanderthal bones from the nearby location of Krapina, one of the most fruitful Neanderthal sites known. At the time I mentioned there was evidence that most Neanderthals were right-handed, but I didn’t really explain why. Now Davorka has sent me two papers (references and links below) that show how we know this. I’m going to write mostly about the Lozano et al. paper (free with the legal UnPaywall app), which tells the tale up to the present. If you can’t get either or both of these papers, email me and I’ll send them.

It is in fact true that about 90% of Neanderthals were right-handed, and that’s the same as present-day H. sapiens sapiens, even though Neanderthals aren’t really the ancestors of modern humans (we do, however, carry some of their genes). That probably means that the common ancestors of our two subspecies—I consider Neanderthals as H. sapiens neanderthalensis, a subspecies of H. sapiens—were also right handed. And indeed, chimpanzees (though not bonobos) are 49% right-handed and 29% left-handed, with 22% of individuals “ambiguous”.

But new data also shows that our ancient ancestors—before the split between modern H. sapiens and Neanderthals, were also right-handed. How did they do this?

It doesn’t come from looking at arm robustness in fossils, for that doesn’t work, nor does it come from looking at brains (as seen in crania), as that doesn’t work, either. It comes from looking at incision marks on the teeth made when a hominin is holding something in its mouth and cutting it—cutting it with the dominant hand. It looks like this (figures from the Lozano et al. paper:

 

Figure 1 [All captions from figures] Demonstration of how marks were likely made on the incisors and canines. A right‐hander pulls down with a stone tool, cutting through the object held between the anterior teeth. Occasionally, when the tool accidentally strikes the tooth’s surface, it leaves a permanent striation on the labial tooth face. Repetitive marking of the labial face allows for the assessment of which hand was used in this bimanual task
Sometimes you’ll hit your teeth with the cutting tool, and the striations (scratches) that this leaves on your teeth—in particular the incisors and canines, but especially the upper incisors—tell you what hand is doing the cutting. Try it!  Imagine you’re holding a piece of meat, or a skin, in your teeth and cutting it with your right hand (if you’re right handed, that’s what you’ll be doing). If you hit your teeth with the cutter (a sharpened stone), it will make a scratch from lower right to upper left, because the tool  will be oriented that way (hold a piece of paper in your mouth and pretend you’re cutting it). If you’re using your left hand, the cuts will be from lower left to upper right. And since you know where in the jaw the teeth are, you can determine handedness if there’s a consistent direction to the scratch marks.

Sometimes the marks will be horizontal or vertical, and sometimes they’ll be made not by humans but by taphonomic (preservation) forces, like sand scratches. You can deal with the latter by using marks only on the front edge, comparing them to those on the rear of the tooth, which should be subject to the same taphonomic modification. Also, you want not he percentage of teeth that show handedness, you want the percentage of individuals that show handedness. To deal with the first and last problem, the authors used these methods:

Thus, striations were separated into four orientation categories: horizontal (H: 0°–22.5°, 157.5°–180°), vertical (V: 67.5°–112.5°), right oblique (RO: >22.5°–<67.5°), and left oblique (LO: >112.5°–<157.5°). This underestimates the number of right or left handers; for example, an oblique mark of 21° would be classified as horizontal, so if the intervals were expanded the tooth being examined would have come from a right‐hander. However, since most studies have not published the raw data and have used the Bermúdez de Castro et al. intervals, we also used them.

Many of the teeth are isolated, especially in the Krapina sample. For this site we used Wolpoff’s reassembled tooth sets, each of which he labeled as a Krapina Dental Person (KDP). His tooth associations were based on similar morphology, occlusal wear, and interlocking interproximal facets, not on the presence of labial scratches. It is unlikely that any of the KDPs in our sample can be grouped together into a smaller number of individuals.

They also tested the “direction” hypothesis by making mouth guards that could be scratched, but also by looking at mouth guards with embedded teeth, as well looking at present day hunter-gatherers and Inuits. These showed directional striations consistent with observed handedness.

Finally, the authors analyzed several samples of hominin teeth: the total sample included five different types of humans (Homo habilis [OH 65, 1.8 million years old], Homo antecessor [from Gran Dolina, 860‐936 kya] the Sima de los Huesos fossils [430,000 years old probably ancestors of Neanderthals], European Neandertals, and modern Homo sapiens).

Here’s the earliest one, the OH-65 Homo habilis, 1.8 million years old. The graph below gives the directions of the scratches, and the predominance of the red bar (right oblique) over the blue bar (left oblique) shows that this individual was probably right handed:

OH‐65 shows a concentration of striations on the labial faces of the anterior teeth. These are visible to the naked eye. Microscopically, they conform to the striations found in much later hominids. The striations are mainly confined to the left and right I1s, the right I2, and right C1. Right oblique scratches predominate, leading to the identification of OH‐65 as a right‐hander. (n = number of striations per category) [Color figure can be viewed at wileyonlinelibrary.com]
The Gran Dolina H. antecessor individual didn’t have enough scratches to be identified but here’s the tooth of a right-hander from about 400,000 years ago (the Sima de los Huesos site):

Here are three Neanderthal teeth with the striations emphasized: the first is a left-hander and the other two right-handers based on the numerical predominance of directionally oblique scratches:

Here’s the final table that tabulates handedness. The earliest hominin was right handed, as were all 15 of the Sima de los Huesos individuals, suggested that by at least half a million years ago, right-handedness predominanted in hominins. The Neanderthals are the ones from Krapina down, and they show a 90% frequency of right-handedness, similar to humans today.

I should add that they also found directional scratches over old directional scratches (the enamel partly heals itself), so the directionality continued throughout the life of an individual, and they find directionality in teeth estimated to be from 10-year-old children as well. Since they didn’t have knives, I suspect much of this involved cutting meat, but also animal skins.

It looks as if since the hominin lineage branched from the lineage leading to chimps and bonobos, we’ve been largely right-handed: about 90%. It would be nice to have earlier fossil data, but this is pretty damn good.  I think the methodology, with its controls and observations of modern humans, is sound. The authors conclude:

We contend that the handedness data reviewed here shows that right‐handedness extends deep into the past of our species. The modern right‐handedness frequencies in earlier European human fossils from Sima de les Huesos and new specimens from the Early Pleistocene of China and Africa suggest that handedness stretches back well before the appearance of Homo sapiens. European Neandertals represent the biggest samples and continue this pattern, showing a right‐to‐left hand ratio identical to that among living Homo sapiens. In our view, the unique 9:1 ratio of right to left handers appears well before the emergence of modern Homo sapiens and is typical of our genus wherever and whenever it is found.

One question remains:

Why does there have to be a dominant hand? Why can’t humans (or those animals that show handedness) be equally dextrous with both hands?

This may be a byproduct of our brain structure (the authors posit that it’s a result of brain lateralization for language or other reasons), or there may be some other reason we don’t understand why one hand must predominate (and it can’t be random because most of us are righties, and there’s a genetic component to that). Who knows? But we do know that most of our ancestors were right-handed—at least according to these data and the data from the Fiore et al. paper.

____________

Lozano, M. et al. 2017. Right-handed fossil humans. Evol. Anthropol. 26: 313-324.

Fiore, I., L. Bondoli, J. Radovčić, and D. W. Frayer. 2015. Handedness in the Krapina Neandertals: A Re-Evaluation. PaleoAnthropology 2015:19-36.

Neanderthal bones in Croatia

October 18, 2018 • 9:30 am

Note: This has been slightly updated after I ran it by Davorka, who caught a few errors.

Over the years we’ve had a number of posts about Neanderthals and their genetic legacy in “modern humans” (see here for a collection), many of them written by Matthew Cobb. Croatia—in particular a hill near the small town of Krapina—is famous for its large collection of Neanderthal skeletons and relics, first discovered during quarrying in 1899. Because there were so many bones, this site afforded a unique look into a population of Neanderthals that lived about 130,000 years ago.

I reported a few days ago on my visit to the Neanderthal Museum in Krapina, which has nice dioramas of Neanderthal life, a cool movie (which, I’m told, was as accurate as possible given what we know about the subspecies), and casts of the bones.

But the bones themselves, and the Neanderthal relics, are carefully sequestered at the Croatia Natural History Museum, where they’re curated by Dr. Davorka Radovčić. My hosts here arranged for me and two of them to visit the Museum. There Dr. Radovčić spent several hours showing us the bones and artifacts, and explaining what they meant and what mysteries still remain (there are many). This required special permission from the Museum, and the visit was one of the high spots of my trip to Croatia. How often do you get to be a few inches away from Neanderthal skulls and teeth, and to hold a spearpoint chipped by one of them so long ago?

You can read more about the Krapina website here. As that article says (I’ve tweaked the English a bit):

. . . a total of 876 single fossil Neanderthal fossil remains were found, placing Krapina in the world”s scientific heritage as the world”s richest Neanderthal finding site.

The Krapina proto-human, scientifically known as Homo sapiens neanderthalensis was discovered in 1899, at the time of geological and panteological explorations at the Hušnjak hill in Krapina started. The excavations lasted for six years, supervised by Professor Dragutin Gorjanović-Kramberger, a famous Croatian geologist, paleonthologist and paleoanthropologost. His works contributed significantly to the European and world science about the fossil man. The half-cave in Krapina was soon listed among the world”s science localities as a rich fossil finding site, where the largest and richest collection of the Neanderthal man had ever been found.

In the sandy deposits of the cave about nine hundred remains of fossilised human bones were found – the fossil remains belonged to several dozen different individuals, of different sex, from 2 to 40 years of age. Numerous fossil remnants of the cave bear, wolf, moose, large deer, warm climate rhinoceros, wild cattle and many other animals were also found. Over a thousand pieces of various stone tools and weapons from the Paleolithic era were found, all witnessing to the material culture of the Krapina proto-human. This rich locality is approximately 130.000 years old.

And the site is here (the dots are other Neanderthal sites):

I’m going to show some of the bones and stones we saw, and explain as best I can remember what they mean.

The collection is stored in several locked metal cabinets, each containing wooden drawers with foam inserts holding the relics. Each drawer is labeled with its contents: “teeth”, “mandibles”, “patellas” (kneecaps), and so on. Here’s Davorka removing a drawer:

The first thing we saw were the crania (skulls), some of which were very well preserved. Notice the labeling of the drawer in the second photo:

This is a particularly interesting skull for a reason I’ll explain in a minute. It’s very well preserved but also has a feature unique among Neanderthal skulls known to science:

Davorka explains some of the features of the skull that set it apart from modern H. sapiens sapiens, and also identify it as a female skull:

You can see the prominent brow ridges and the upper part of the skull, which bears the cool feature:

This skull, of a young adult female (probably in her 20s or early 30s; you can tell the sex from the way the skull is shaped), has a series of 40 horizontal incisions made in the forehead at or soon after death (they aren’t healed). Their purpose isn’t known, but it seems likely it was involved with some kind of postmortem ritual, perhaps indicating a respect for the dead or even something associated with an idea of the afterlife. We simply don’t know, as Davorka emphasized. Below are two photos of the incisions and a brief video of Davorka explaining them:

 

Davorka explains the cuts in this video: they weren’t made to butcher or scalp the woman:

Neanderthal DNA is extracted from the middle ear capsule, as it is tough and well insulated from the environment. I erred in an earlier post in saying that DNA has been extracted from Krapina Neanderthals; Davorka tells me that Svante Pääbo and his colleagues extracted it from another Croatian Neanderthal site called Vindija.

We now know that Neanderthals interbred with “modern” humans (H. sapiens sapiens), and that the average non-African human carries about 3% of their genome from Neanderthals, including genes now used in the immune response. Although the offspring in at least one direction of the cross must have been fertile—for that’s the only way Neanderthal DNA could get into H. sapiens sapiens—we don’t know if offspring from both directions of the cross were fertile. For example, we haven’t found mitochondrial DNA from Neanderthals in modern humans. That could reflect either accidental loss of mitochondria, selection against mitochondrial DNA that did infiltrate modern human populations, or the sterility of offspring between Neanderthals mothers and H. sapiens sapiens fathers.

The middle ear capsule is at the upper left here, just above the red lettering that reads “88.11”. That’s the precious bit for paleogeneticists:

Mandibles! The teeth are relatively larger than ours, and the jaw has more space to accommodate all the molars, so the “wisdom teeth” are not crowded as they are in modern humans.

Two lower jaws (mandibles); note the rotation of one tooth in the left row of teeth:

The “rotated” tooth between the two white-ish ones. I can’t remember what the significance of this was, but I wrote to Davorka who said that some feel it’s due to genetic relationship and possibly inbreeding:

The scientists who worked on this concluded that they rotate due to “biological origin, an inherited condition common in the Krapina people. . . The sample is too small to for the observation to have significance, but we believe a hypothesis of biological relationship among the individuals found in Krapina levels 3 and 5 can be proposed to explain our results. Such a hypothesis is supported by the unusual superior deflection of the internasal suture in the only three Krapina specimens to preserve the suture” (Rougier et al. 2006; you can see the whole article in the book New insights on the Krapina Neandertals, pp. 43).

The jaw of a young (probably 6-7 year-old) Neanderthal, showing the deciduous teeth (“milk teeth”) and the three adult teeth that haven’t yet erupted. Neanderthals didn’t live very long: a 40-year-old individual was old:

Unfortunately, some of the mandibles were cleaned, removing the precious calculus (hardened plaque that the dentist scrapes off of your teeth at cleaning time). Davorka explains in the video how that cleaning caused the loss of precious biological information. Note the “retromolar space” giving ample room for all the molars.

Teeth, including a “shovel shaped” incisor, different from the shovel-shaped incisors found in Asian specimens of modern H. sapiens.

A well preserved molar:

A shovel-shaped incisor.

The wear patterns of these front teeth indicate that the Neanderthals held items in their teeth while processing them, like holding a skin in your mouth while scraping it with your hand. The position of the wear marks also shows that about 80% of Neanderthals were right-handed, scraping with their right arms while holding the item in the left side of their mouth. Isn’t that cool? In fact, this is about the same proportion of right-handers in Croatia today:

Arm bones. A drawer full of humerus (upper arm) bones:

This is an ulna (one of the two lower arm bones) that has been chopped off and then healed, indicating that the individual lost part of his or her arm. Then it healed after the injury, so the individual survived missing a hand:

A drawer full of kneecaps. They are lighter than kneecaps that are “fossilized”, as the sandstone has probably leached out many of the bone constituents:

A smashed leg bone (tibia), either trod on soon after death or smashed during death, perhaps during hunting or warfare. (Neanderthal bones show much less frequency of “warfare” damage than do the bones of earlier hominins like australopithecines. They seem to have been a peaceful subspecies.)

This Neanderthal shows a healed bash in the head (the dent in the center, which didn’t penetrate the skull), along with lines surrounding the wound. Life was tough for these hominins!

Here Davorka explains that we’re not sure what the lines are: they could have been deliberately incised (trephination) to relieve pressure on the wound coming from pus, or perhaps the lines  could be just a taphonomic (preservation) artifact.

Neanderthals were largely carnivores, though we know they also used medicinal plants. They ate bears, beavers, and even rhinos. Here’s an adult rhino that I believe was killed by the Krapina Neanderthals. They would of course have had to hunt in groups, and it must have been very dangerous to spear a bear or a rhino to death.

They apparently killed birds, too, as bits of bird skeletons, with some of the parts modified, are found in association with the Neanderthal bones. Here are some talons and foot bones from the white-tailed eagle, Haliaeetus albicilla, a species that is still around.

There are cut marks in the talons and foot bones to which they were attached, suggesting that Neanderthals were using the talons and bones as jewelry. This is supported by recent findings of gut “fiber” tied around part of a talon. Here are a foot bone and a talon that have been modified by having grooves cut in them.

This is a toe bone to which the talon was attached. See the cut groove at the lower end?

Modified eagle talons:

Davorka is pointing to the human-cut groove:

Here’s a paper (click on screenshot to read) in which Davorka and her co-authors suggest the use of talons as jewelry:

A bowl full of Neanderthal tools:

I got to hold a beautiful 130,000 year old Neanderthal spear point, chipped out of flint:

I previously described the tool below as a “scraper”, but I remembered wrong. As Davorka tells me, it’s not a tool, but something even more interesting. It’s a piece of “mudstone” that was probably picked up and brought to the Krapina site because it is a curiosity: it has “ichnofossils” in it (traces of living organisms, like worms, that have modified the sediments). Of course the Neanderthals didn’t know what these were, but might have been so impressed by the unusual patterns of this rock that they decided to keep it.

And Davorka and I after our visit. It truly was one of the great experiences of my life, and I’m immensely grateful to Davorka for her instruction and kindness, and to my hosts, Igor, Damjan, Darko, and Pavel, for arranging this visit. (We all went to lunch after this, but more on that in another post.)

 

 

A very old tool

October 16, 2018 • 2:00 pm

Here’s my hand holding a 130,000 year old flint spearhead created by a Neanderthal living near what is now Krapina, Croatia. It’s a beautiful point, and amazing to think that this was chipped by a hominin so long ago.

I learned a ton today at the Croatia Natural History Museum, as we had a special visit to the Neanderthal collection and got a close-up view of the stunning bones and artifacts. This required special permission, and I am most grateful to the curator, Dr. Davorka Radovčić, for taking the time to show us the specimens and give us detailed explanations.

I will do a whole post on our visit, with lots of cool photos, but here’s a teaser:

Okay, one more. This is a very special skull (all bone, no reconstruction), but I’ll tell you about it later: