Degenerate Hobbits

There’s a new report out, claiming that the Flores Hobbits are probably an island dwarf version of Homo erectus, judging by their teeth.

Flores isn’t a very big island – ~5,000 square miles, similar to Connecticut. There couldn’t have been many hobbits. And they seem to have been there for a long time, hundreds of thousand of years, judging from tools found.

Which means that if they were what they seem to be, they would have suffered far more from genetic load than Neanderthals or Denisovans. All those problems of slightly deleterious alleles drifting to high frequencies would be much more serious, and the probability of salvage mutations would be much lower.. Moreover, the Flores Hobbits look screwed up (unlike Neanderthals), with many skeletal anomalies and asymmetries. This is why some anthropologists have argued that they are just diseased modern humans.

Point is, the island-dwarfed erectus story does makes sense, but it would inevitably result in them being highly screwed up. Like they are. I talked about this several years ago – “Back to the Trees” – and suggest that they might have suffered from partial mutational meltdown – too much load to have an efficient brain. The skeletal anomalies suggest that their load was pretty serious.

Advertisements
This entry was posted in Uncategorized. Bookmark the permalink.

36 Responses to Degenerate Hobbits

  1. MawBTS says:

    So if that’s accurate, then these tribes…

    https://en.wikipedia.org/wiki/Uncontacted_peoples

    …Are basically just genetic load factories. Some of them just haven’t had enough time for obvious problems to manifest yet.

    • st says:

      Which, if true, might explain the average IQ discrepancy between the contemporary hunter-gathering tribes and the rest of the world, noted by d-r Cochran. This would also mean that prior the the invention of agriculture not all hunter-gathering tribes had to be dumber than their agricultural offsprings.
      But isn’t the notion of reproductive isolation generating degradation go against the evidence in the face of Ashkenazi Jews (if d-r Cochran is right about them), Finish (homogenous, isolated and having the smallest genetic load in Europe) or the Japanese people. Something to do with the time-scale and severity of isolation – or the low population size? Would the mutational meltdown had happened if there was selection pressure against it? (tigers, apes competing for the same niche, etc?). Back to neanderthal gene toxicity perhaps they are still being purged from HS nowadays, since the reproductive rates of eurasian HS seem somehow smaller lately comparing to the rest of the world, especially the reproductive rates of eurasian HS. I guess the declining fertility of the west should be regarded as continuation of genetic purging that selection pressure started right after neandertal introgression. Heard that caucasian females in reproductive age are less than 2% of the total human population nowadays. I do not know if it’s true, but if it is, that’s less than the neandertal heritage in the average contemporary eurasian, which is 3%. Darn genetic purging, or else.

      • Anonymous says:

        It is all about population size. A totally isolated population, that goes through a bottleneck, will be fine if enough people get through.

        They have formulas for this, which are used at seed banks to determine how many seeds need to be frozen to maintain 99% of a population’s genetic diversity at each generation.

        If you keep a large enough amount at each generation, then selection will maintain the better alleles no matter. It is only when the population gets too low that really bad things happen.

        But really interesting things also happen. Which is why isolated islands are interesting for evolution studies, but not for robust species. I don’t think giant tortoises will be killing off rats any time soon.

      • gcochran9 says:

        So confused. The Ashkenazi went through a bottleneck – I think almost certainly during their colonization of the Rhineland – but their numbers expanded rapidly after that. They weren’t isolated for hundred of thousands of years on a tiny island!

      • rkr says:

        I always thought half-Jews were vastly over-represented among prominent scientists of the 20th century compared to their ratio vs full Ashkenazi Jews(who were, of course very prominent themselves). Finns are neither homogenous nor isolated but we tend to share longer blocks of DNA than is typical for other Europeans of this millenium except for the Icelanders and Ashkenazis and probably Romani Gypsies. This doesn’t necessarily equal a high overall homozygosity(for Finns at least) but if you happen to have bad luck you can have a large number of harmful recessive alleles on the same genetic region.

    • gcochran9 says:

      Nobody has had that much time.

    • IC says:

      How about Amish population? Is pop large enough? Any genetic inflow into population? We all know there is constant outflow from Amish. Any load study on them?

  2. IC says:

    “many skeletal anomalies and asymmetries” – sign of mutational load

    Physical beauty is critically important in sexual reproduction. Your species depends on it. In the world of sexual reproduction, physical beauty ranks supreme in the hierarchy of all factors (as shown in previous post).

    • IC says:

      Just love science. A process of learning, discovering, changing, finding truth. Never static like ideology, or faith based stuff. Well some people treat their pet theory like static process and defending it like theology in face of all new contradictory evidences. That theory will be their faith/or religion at end.

      • IC says:

        Most remarkable thing is that some people pigeionhole everything into their pet theorly just like those ideologues who pigeonhole every thing in the world into their ideology doctrinces.

  3. dearieme says:

    Poor wee buggers. Is one allowed to say that of our distant, distant cousins? I do anyway. Poor wee buggers.

  4. The island of Flores is one weird place, it doesn’t look geographically like an end of the earth, just one in a long line of islands, but the oddball animals that evolved and survived there make it seem so. We have the hobbits, we have Komodo dragons, and up to the time of modern man, rats the size of dogs and pygmy elephants. The one complete skull of a Flores hobbit had an asymmetrical skull, a clear sign of serious genetic problems. Humans are obsessed, absolutely obsessed with facial symmetry when selecting a mate. Obviously some of this is cultural, but not all, we are evolved to seek a healthy mate just like every other species.

    Cool stories about the hobbits. The locals have a folk memory of them, they call them the ebu gogo, with means the grandmothers who eat anything. The females had long floppy tits that they could throw over their shoulders. They claim they killed the last ones about the time the Dutch arrived. Mind you these are people who sat around a lot and had nothing better to do than bullshit each other, but it’s good bullshit so I thought I’d share it.

    Native people do have folk memories going way back that can be accurate so who knows for sure how long the hobbits survived. If there were pygmy elephants on the island there certainly could have been a pygmy or dwarf Homo Erectus that survived there too. The locals even claim the hobbits still survive on other uninhabited islands in the area. No doubt sooner or later the bogus Discovery Channel will have an expedition to go looking looking for them. They are about a hundred times more likely to really exist than bigfoot. But I guess it’s easier to go look for an eight foot bigfoot behind a barn in Oklahoma that a three foot Hobbit on an uninhabited island on the other side of the world. They are gone but hopefully in one of the limestone caves on the island lies a tooth or a finger bone with preserved DNA.

  5. TWS says:

    If it happened once could it have happened more than once? Are there islands or perhaps places now under water where we might find more recent anomalies like these little island dwellers? And how in the hell did they get there? Did erectus have boating capability?

  6. pyrrhus says:

    Absent evidence of external forces causing extinction, genetic load seems highly likely as the cause…Mouse Utopia in the Pacific.

  7. Just as strange and incongruous as the Homo Floresiensis discovery ( a 13,000 year old dwarf Homo Erectus) or the link between living people in Austronesia and a Denisovan pinky bone found in Siberia is the treasure trove of newly discovered Homo Naledi bones in South Africa.

    It is like you can’t make this stuff up, it would be too silly. It sure looks to me that the only way that Homo Naledi hauled 15 dead ancestors way down deep in a cave system 100 meters below the surface and so far into a cave system that no animal could follow the smell of the rotting carcasses for a good meal was to control fire. Only problem is Homo Naledi had a really tiny brain and developmentally (no age has yet been determined) he looks to be two to four million years back in time developmentally. I mean WTF. Incidentally they are saying at this point there had to be a closer entrance that has since closed up, but they don’t know and neither do I. But if those smelly rotting carcasses had been anywhere close to an outside opening keen nosed critters would have found them and chewed them up and they never did.

    I don’t know what to think, just asking what’s up with what the the experts think about Homo Naledi.

    • IC says:

      Is it possible that water washing the bodies down?

    • Could it be that Homo Naledi navigated its way through the cave in the dark? If the intention—or instinct—was to dispose of a carcass, maybe a torch was not necessary. A dead body could have been transported as far as possible—the further the better, so there would be no odor of decay detectable by the tribe or its predators. The undertakers could have then retraced their steps, back through the tunnel, to exit the cave.
      What’s to keep one them taking a fall, or getting lost? Maybe that happened occasionally…?

      • Nope, but just my best guess, nobody really knows. If you have you ever gone cave exploring you need light to get far into a cave. It is pretty safe to assume these Homo Naledi controlled fire. Once you assume that, and it is a pretty safe assumption, then we have a revolutionary perspective on just how ingenious our early ancestors were way way earlier in our evolution than anybody presumed.

        We have a veritable treasure trove of bones from this one site from a period in hominid evolution when we had next to nothing. They appear to be two million years old IF you try to place them in the appropriate spot on evolution time frame but that could be way off. Look at this oddball dwarf homo erectus for example, he doesn’t belong existing near the present, but that is when he lived.

        The Homo Naledi discovery will shake our lousy guesses on human evolution to the core just like three other discoveries did. 1) Homo Florsiensis 2) Our 3% Neanderthal ancestry and 3) our Denisovan sidekicks. Now I will shut up on this subject till our fearless leader brings it up on his own, and he will.

        Don’t go looking at their pinhead brains, look at their piano playing hands 🙂 there I go again, getting silly. Anyway this little corner of science should be a delight to follow for a long time to come. It is moving forward.

  8. IC says:

    http://www.bbc.com/news/science-environment-34809804

    Here is DNA stories from London. We are in the age of discovery with new tech (not gun boats).

    • dearieme says:

      That tale drips with PC. London was a Roman foundation, so that it follows that many of the early inhabitants would be Romans, who might have come from anywhere in the the Empire. To find that that was so is a rather feeble result. If they’d found no evidence of anyone from the Continent, or the Near East, or North Africa, that would be a result worth fussing about. It’s as if you’d studied remains from the early population of Philadelphia and expressed surprise that they’d grown up in Britain. Did I say “PC”? “Deceit” might be nearer the mark, given the spin put on it.

  9. ohwilleke says:

    Island dwarf-erectus would make a lot of sense, but for the Papuan-Aborginal Australian association with Densiovan DNA, which given the location of H. Florensis make a strong circumstantial case for hobbits being Denosivans or dwaft Denisovans. Another possible Denisovan trace may be the swath of post-H. Erectus tools found in parts of Asia that never saw Neanderthals that runs more or less due North-South on a path running roughly through western China that could be the critical link between Siberians and island SE Asians. Denisovan should have appeared in the waning days of H. Erectus, so they would have favored territory that was inaccessable to H. Erectus or undesirable to H. Erectus so that they could control relatively virgin territory.

    Re: H. Nedali I am inclined to credit the investigators interpretation of the site as not a product of flood waters. Intentionally piling dead bodies in one place doesn’t seem so remarkable or necessarily implicating high IQ. I’m inclined to think that the observed site may have been a place that the sick went to die in peace, a bit like cats tend to find tucked away places, like under a porch, to go when they are dying. The instinct of a vulnerable person to seek a place of safety to avoid being eaten alive by predators seems more likely to me than symbolic burial practices.

    • gcochran9 says:

      Since some of the tools found on Flores are ~800 k old, and since the teeth (and some other features) look like homo erectus, probably a dwarf erectus.

      • ohwilleke says:

        This is fair, but Denisovan genetics suggest that they aren’t H. Erectus because their split from the Neanderthal clade is too young. But, (1) the coincidence of the appearance of Denisovan admixture in modern humans with the location of island of Flores and (2) the fact that H. Flores and modern humans co-existed more or less peacefully on tiny Flores for something like 40,000 years (much longer than any period of modern human-Neanderthal co-existence in Europe), argue strongly for modern human-Denisovan admixture in and around Flores in that time frame and for H. Florenesis being the source of the Denisovan admixture.

        A more complex scenario could reconcile the seemingly contradictory indications of the evidence. For example, maybe Denisovans replaced H. Erectus on Flores, with significant H. Erectus admixture that influenced H. Florensis teeth and other features.

  10. Neocolonial says:

    Saw this article http://www.statnews.com/2015/11/23/malaria-mosquitoes/ regarding the introduction of a GM mosquito that doesn’t transmit malaria, tooled up with what the article calls a ‘gene drive’ that ups the transmission rate to offspring from 50% to 97%.

    What caught my attention was the comment “Ordinarily, as genetically engineered mosquitoes mate with regular ones, traits like antimalaria antibodies are inherited by only half the offspring. The new genes eventually get washed out.”

    Wouldn’t they only get washed out if there wasn’t a competitive advantage to the trait?

  11. RCB says:

    I hadn’t heard of mutational meltdown as an explanation of insular dwarfism – if that is what you are suggesting here. Mutational meltdown / drift is not mentioned on the wiki page, for what little that is worth (https://en.wikipedia.org/wiki/Insular_dwarfism). It’s totally reasonable, although I would guess that it must operate much more slowly than selection.

    Re: “All those problems of slightly deleterious alleles drifting to high frequencies would be much more serious, and the probability of salvage mutations would be much lower”
    I’m trying to get a loose intuitive grasp of mutation meltdown dynamics. Specifically: the probability of fixation (given an allele has already arisen) always increases at lower pop sizes, for both good and bad alleles. So why should that end up being a bad thing for the population – i.e. why mean fitness decline? Here’s my very back-of-the-envelope calculation:

    (1) We know that the rate of fixation of neutral alleles is the rate at which they arise times the probability that they fix. This is (Nm)(1/N) = m. That’s a classic neutral theory result.
    (2) For beneficial alleles, we can loosely write the probability of fixation as (1/N + s_b), where s_b provides the (positive) difference between the actual probability of fixation and the neutral probability. This is not actually a constant – it will depend on N – but let’s ignore that for now. Then the rate of fixation of beneficial alleles is (Nm)(1/N + s_b) = m + N m s_b. This is positive in N; larger population sizes increase rate of fixation for beneficial alleles (as Cochran has said many times).
    (3) For deleterious alleles, use a similar convention to get (Nm)(1/N – s_d) = m – N m s_d. s_d is something like the selection coefficient against the deleterious allele (again, not constant in N). This is negative in N, opposite from above.
    So, although smaller populations always increase the probability of fixation for any allele given that the allele has already arisen, the overall rate of fixation is behaves differently.

    This would all break down if the s parameters were of order O(1/N) or worse. So I checked with actual pop gen theoretical results to make sure I wasn’t fooling myself. Kimura has the theory for this: http://www.genetics.org/content/65/3/525.full.pdf
    P(fixation of new allele) = (1-exp(-4 N_e/N s))/(1-exp(-4 N_e s))
    Multiplying that by N m gives you the rate of fixation of alleles of selection coefficient s. And it all checks out: this rate always increases with N if s>0; always decreases with N if s<0.

  12. the mediocre middle says:

    Is their any chance island dwarfism is an adaptation to inbreeding, or is their a superior theory that rules that out?

    • Boris Bartlog says:

      I’m not sure it’s possible to ‘adapt to inbreeding’, but if it is, I wouldn’t expect it to be by way of some macroscopic phenomenon. We could however imagine a bit of a selection effect. If there were two initially identical (small, isolated) breeding populations, one of which randomly fixed a variant for larger size and the other for smaller size, the latter population would maybe be more likely to persist in time, because it would end up having a larger breeding population.
      In reality I would not expect such an effect to be detectable. Since we see both island gigantism and island dwarfism, I expect the explanation(s) will rely on the particular details of each situation.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s