|Evolution in the News - November 2017|
|by Do-While Jones|
How big was the Missing Link?
In keeping with this month’s theme of scientists telling tall tales that please their sponsors, we offer this rather technical analysis of the size of the Last Common Ancestor (LCA) between apes and humans.
We put this one last because we know many of our readers will get bored with it and just skip to the end. Skimming through it is OK, as long as you promise to read our conclusion at the end.
You don’t have to try to understand it. Just notice how the authors try to baffle you with buzzwords. Remember, they are analyzing the characteristics of an animal for which there is no evidence of existence. They just believe it must have existed because, well, it just must have existed if the theory of evolution is true.
Why is the size of the LCA important? They think it has a bearing upon whether the Missing Link between apes and humans swung from trees (that is, was “suspensory” in their jargon) or was a knuckle-dragger (“terrestrial”) who eventually attained upright posture.
Here are some excerpts from this very long, technical article.
Body mass directly affects how an animal relates to its environment and has a wide range of biological implications. However, little is known about the mass of the last common ancestor (LCA) of humans and chimpanzees, hominids (great apes and humans), or hominoids (all apes and humans), which is needed to evaluate numerous paleobiological hypotheses at and prior to the root of our lineage. Here we use phylogenetic comparative methods and data from primates including humans, fossil hominins, and a wide sample of fossil primates including Miocene apes from Africa, Europe, and Asia to test alternative hypotheses of body mass evolution. Our results suggest, contrary to previous suggestions, that the LCA of all hominoids lived in an environment that favored a gibbon-like size, but a series of selective regime shifts, possibly due to resource availability, led to a decrease and then increase in body mass in early hominins from a chimpanzee-sized LCA. 1
This follows the common format for technical articles. They begin by saying that what was previously published before is wrong, and their new idea is right.
Though the timing, causes, and biological implications of the increase in body mass that took place during human evolution continue to inspire a wealth of research (e.g., refs. 1,2,3,4,5), the body mass of the last common ancestor (LCA) of chimpanzees and humans remains unexplored in any rigorous fashion. This omission is startling because numerous arguments over one of the most contested topics in hominin evolution—what were the selective regimes that led to the origins of bipedalism (but see ref. 10)—depend on inferences about body mass at and prior to the root of our lineage. Various classic models proposed a body mass increase as a proximate factor in the evolution of suspensory adaptations and the transition from an arboreal to terrestrial hominid (great apes plus humans and our fossil ancestors) as larger sizes dictated a switch between locomotor modes, while models based around an arboreal quadruped ancestor (e.g., ref. 14) implicitly assumed a smaller-body mass in order to maintain balance and stability on deformable branches of different diameters. Note that here we define body size as body mass. 2
The “most contested topic in hominin evolution” is whether the LCA lived in trees or on the ground. It is contested, of course, because there is no scientific proof one way or another, despite what you were taught in public school.
One important reason for this omission is the paucity of African fossil hominids during the period when the chimpanzee and human lineages are believed to have diverged, perhaps 4–6 Ma (million years ago) or earlier at 6–8 Ma, with the notable exceptions of putative basal hominins Orrorin tugenensis (~6 Ma), Sahelanthropus tchadensis (6–7 Ma), Ardipithecus kadabba (5.5–6.4 Ma), and the later Ardipithecus ramidus (4.4 Ma). In addition, body sizes in the more well-sampled Miocene hominoid (all living and extant apes and humans) taxa (e.g., Proconsul) appear to be extremely variable (e.g., refs. 24, 25), and questions about how these species relate to one another and to crown hominoids (reviewed in ref. 26) further complicate the usefulness of these data. 3
This is an example of the second characteristic of the common format of evolutionary arguments. Specifically, the “paucity” (lack) of fossils, and their “putative” (questionable) interpretations. The fossils are “extremely variable” with no orderly pattern. These excuses are made to give them cover when later articles prove them to be wrong. They did the best they could with the inadequate data available at the time, so it isn’t their fault that they were wrong.
However, a few recent findings argue caution with acceptance of a chimpanzee-sized series of LCAs stretching back to before the divergence of hylobatids [gibbons] from other hominoids [human-like creatures] around 19.5 Ma. First, this hypothesis coincides with the assumption of an overall chimpanzee-like morphology for the chimpanzee–human and hominid LCA, a topic of much debate, with some researchers suggesting that current fossil evidence and analyses point to a generalized monkey-like ancestor. Chimpanzee-like postcranial morphology and body mass are not necessarily linked, although this is often implied by many models that suggest a chimpanzee-like LCA. Second, the description of Pliobates cataloniae, a small-bodied (4–5 kg) hominoid from the Miocene of Spain (11.6 Ma), argues for a gibbon-sized common ancestor of all crown hominoids, rather than an extant great ape-sized ancestor with hylobatids evolving as a dwarfed lineage. Finally, a large-scale analysis of hominin body mass found earlier hominins were smaller-bodied than previously thought (Table 1, Supplementary Table 1), with no evidence for an orderly increase in body mass from Australopithecus to early (non-erectus) Homo to Homo erectus as has been suggested. Average body mass for the well sampled Australopithecus afarensis was ~5 kg less than an average common chimpanzee, and many other well sampled later hominin taxa (Australopithecus africanus, possible Paranthropus boisei, Paranthropus robustus, Homo habilis sensu stricto) are ~5–10 kg below Au. afarensis (Table 1). While body mass predictions for the earliest undisputed hominin, Australopithecus anamensis (46.3 kg), and the earliest putative hominins O. tugenensis (35–50 kg), and the later Ar. ramidus (~50 kg) (but see refs. 3, 7), are all in the range of common chimpanzees, these estimates are based on single fossils, and overall these findings argue that the pattern of body mass evolution in our own lineage may be more complicated than either stasis or a steady increase in body mass from a chimpanzee-like ancestor. Taken together, while a chimpanzee-sized LCA has been hypothesized as the phenotype from which all hominoid branches diverged, to the best of our knowledge this has not been tested in any quantitative, phylogenetically informed fashion. In addition, the data underlying these hypotheses appear to be problematic and further compounded by poor understanding of the Miocene fossil relationships, and likely heavily influenced by the view that chimpanzees provide fairly clear windows into our evolutionary past (see Supplementary Note 1 for taxonomic scheme used here). 4
As is typical, the article is full of weasel-words. One needs to be “cautious” about “acceptance” of “assumptions” about “topics of debate” which “suggest” things which are “not necessarily linked” but “often implied.” Things that were “previously thought” are based on “no evidence” and are just “estimates” that “have not been tested” and are “problematic” because they are “poorly understood” and “heavily influenced” (that is, biased) by a previous “view.”
The article continues with a very boring, technical explanation of their methods of analysis. We are not so cruel as to make you read it. (Gluttons for punishment may use the link in the footnotes.) Let’s just skip to their conclusion.
The results of our novel comparative phylogenetic analysis of body mass evolution in primates have large consequences for the paleobiology of hominoid and hominin origins. First, our results suggest that the LCA of chimpanzees and humans lived in an environment that favored a body mass similar to modern chimpanzees (either Pa. troglodytes, Pa. paniscus, or both depending on the data set used), and this optimal body mass was shared with the earliest hominins. Consistent with fossil evidence of large body sizes, our results support earlier suggestions that this LCA had a body mass close to that of modern chimpanzees. It should be noted that this regime persisted in the earliest hominins until shifting to a smaller-bodied regime near or following (depending on the data set used here) the origins of Au. afarensis at 3.77 Ma. While this reduction in the optimal average body mass could be due to a reduction in female body mass resulting from differential effects of ecological stresses—such as caused by climate variability at Hadar 3.4–2.9 million years ago—recent findings suggest that later early hominins from South Africa (Au. africanus, P. robustus) were smaller bodied both on average than earlier Au. afarensis, and purported males may have had a slightly larger decrease in body mass than females (~4%). Thus, if an increase in sexual dimorphism in Au. afarensis was the result of ecological stresses affecting females to a greater extent than males (e.g., refs. 47,48,49), it appears that these stresses affected the sexes in a more similar manner in later australopiths. In fact, the estimated optimal body mass for the later smaller-bodied early hominin regime was slightly below 30 kg (Table 2), which is about 10 kg smaller than the earlier Au. afarensis, and later early hominins (starting with the 30.5 kg Au. africanus at 3.03 Ma), including the small-bodied H. habilis, appear to be evolving towards this new smaller optimal body mass. The origin of Au. africanus coincides with the shift towards more open environments after 3 Ma in South African sites, as well as apparently increased greater climatic variability in East Africa, which likely imposed new selective pressures on early hominins and led to a regime shift at this time. The regime shift to larger optimal body sizes near the origins of H. erectus (Fig. 1b, c) as well as larger body mass in this taxon (Table 1) could signify the combination of environmental changes to more favorable conditions or behavioral differences leading to shifts in the ability to use available resources (e.g., a greater reliance on high-quality sources such as meat). Of course, this sequence of body mass evolution (and the results of this analysis) depends on the relationships among taxa, but at the very least there appears to be a substantial decrease in both the species average as well as average male and female body mass for hominins between 3.0 and 2.0 Ma with the extinction of Au. afarensis. It is also suggestive that the optimal body mass for the regime that contains H. heidelbergensis and H. neanderthalensis is slightly below the average mass of G. gorilla and G. beringei in almost all iterations here, and these hominins may in fact be evolving toward a selective regime that favored increasingly large body sizes due to factors such as colder climates or hunting larger-bodied prey. No doubt hominin body mass was constrained and influenced by a wealth of factors, such as sexual selection, food availability and other ecological influences, tool-use, and physiological constraints that are not tested in the current model.
Second, our results indicate that the LCA of all hominoids shared a selective regime with hylobatids and was likely the mass of a modern gibbon, arguing against the view that hylobatids are a dwarf lineage from a great ape-sized ancestor of all hominoids (e.g., ref. 29). Larger mass apparently did not evolve until after the divergence of hylobatids, with two regime shifts to increasingly larger body mass optima prior to the LCA of hominids. While we include stem ape Pliobates cataloniae in our main analyses, our findings without Miocene ape taxa (Supplementary Fig. 3) independently support Alba et al.’s recent claim, and earlier suggestions of a gibbon-sized ancestor of hominoids based on the type specimen of Pliobates cataloniae. We also note that this body mass regime is also shared by the majority of Old World Monkeys and by the distantly related New World Monkey family Atelidae, and may be the plesiomorphic (ancestral) condition for catarrhines. While it was suggested that that suspensory behavior in hominoids evolved as a necessary locomotor shift coinciding with increasing body mass, a gibbon-sized ancestor of all apes argues against this hypothesis—it could be that antipronogrady first evolved in a gibbon-sized early ape, further adapting in the lineage that led to hylobatids. An adaptive shift favoring a larger body mass could have led some early hominoids—already adapted to a rudimentary form of suspensory locomotion—to adapt their morphology and behavior to deal with this change, leading to some of the differences between great ape and gibbon locomotor behavior. In this model, there is no need for the independent acquisition of suspensory behavior among the hominoid lineages—the series of morphological changes that allow for suspensory behavior evolved once and the combination of continued use and possibly phylogenetic inertia (resistance or slowness in adaptation) in these characters led to their persistence while body mass appears to be extremely evolvable in this clade. Taking a step back, suspensory behavior and increased body mass have been argued to be hominoid adaptations to a foraging strategy allowing them to compete with increasingly numerous old world monkeys since the Middle Miocene (reviewed in ref. 60). Our results suggest that these two adaptations occurred independently of each other and could have been part of an arms race with monkeys for fruit resources—suspensory behavior to access ripe fruit on compliant branches at the edges of foliage evolved first, followed by larger body sizes when direct physical competition was required. Sexual selection in hominids likely further increased optimal average body sizes. We also note that although hominin and hominoid evolution is the focus of this analysis, our complete results suggest that the basal euprimate lived in a selective regime that favored an optimal body mass between 1.4 and 1.6 kg (e.g., Fig. 1). Though this estimate is close to previous suggestions, it is far above an analysis that included body mass estimates for early primate fossils (~55 g) (but see ref. 62).
Finally, our results provide evidence of a complex and changing adaptive landscape in the hominin and hominid clades—while almost all other primates are evolving toward two body mass optima in our sample (e.g., 1.4 and 7.0 kg; Fig. 1a), hominids (including proconsuloids) had a substantially greater number of adaptive optima due to distinct regime shifts than any other group (Fig. 1c). While these results are preliminary, they suggest that most of primate evolution has taken place within a small number of ecological niches—one small-bodied regime principally based around arboreal quadrupedalism and leaping, one larger bodied regime, members of which evolved toward suspensory behavior (Hylobatidae and Atelidae) and continued arboreal quadrupedalism and leaping (most Cercopithecidae). Larger-bodied species adapted to terrestrial locomotion—Pa. cynocephalus and Pa. anubis here, are near their own body mass optima (Regime “k”—17.7 kg; Table 2). Within each group is variation in locomotor behavior, as well as diet, social structure, and so on—differing local selective pressures that likely led to the variation around the optimal body mass within a given regime. Together, the greater number and greater complexity of body mass optima for hominids and hominins supports the hypothesis that dramatic and uncommon shifts in the adaptive landscape drove human evolution. 5
We regret that we had to subject you to so much boring, technical material—but we wanted you to see for yourself that their lengthy conclusion is nothing more than speculation about what could have happened, and why it may have happened.
Real science is conclusive. The experiments produce the same results no matter who does them. There is no speculation about what happened.
Fake science uses scientific terminology to appear scientific. It is academic identity theft in an illegitimate attempt to give scientific credibility to a fallacious philosophy.
Real science has value because it accurately and reliably reveals the truth about the world we live in. Knowing how things work allows us to succeed by working with nature, and prevents us from trying to violate absolute physical or biological laws. Real science has real value.
Many of the things that make life better are simply copies of natural designs. Radar and sonar are human applications of the echo location used by bats and whales. Birds had wings long before airplanes did. Even something as simple as Velcro is patterned after biology.
Because it is built on a lie, fake science doesn’t make life better. Physical laws cannot be violated, no matter how skillfully the lie is presented. The laws of nature don’t change because of anything a silver-tongued scientist says.
In our feature article, we gave an example of how photographic data was manipulated to present a false view of nature because it advanced National Geographic’s belief that animals and humans are equal. Even if animals and humans are equal, it does not justify taking misleading photographs in order to secure funding.
The “scientific” explanations of how giraffes got long necks, how oxygen got to the moon, and how much a mythical ancestor weighed, are just stories posing as science. These stories are designed to advance an agenda unethically.
Exposing fake science does not make us anti-science—we are promoting real science. Real science doesn’t have an agenda, other than to discover and explain natural laws (which cannot be violated).
There are economic, religious, and political agendas behind the Theory of Evolution.
The economic agenda is driven by the religious and political agendas. People with religious and political agendas spend money on scientists who will produce quasi-scientific arguments that support their agendas.
Universities depend upon research grants. People with a political or religious agenda will pay for research that “proves” that the theory of evolution is true. In order to keep the stream of money flowing, it is necessary to produce papers which satisfy sponsors while leaving the door open for further research.
There are people who are afraid of a judgmental god, and they need to disprove the existence of the God of Abraham to calm their fear. To do that, they need to disprove the book of Genesis. They need to establish an alternative to the Genesis account of creation which does not involve a supernatural force capable of inflicting punishment on sinners. The theory of evolution is such an alternative.
There are people who believe that man is no better than animals, so animals should have equal rights. The theory of evolution supports that belief.
There are people who believe that Mother Earth is alive, and that people are hurting her. The theory of evolution supports the notion that natural processes make things better, and unnatural human activity makes things worse.
Historically, there has always been a power struggle between the church and the state. Leaders of the state would like to weaken the opposition from the church. In the United States, the various branches of Christianity have the most voters. Since Christianity has political power, it must be defeated so that political leaders can make decisions unopposed.
The support for evolution is not really based in science. As we have been showing for more than 20 years, science is against evolution. The theory of evolution starts with abiogenesis (the spontaneous generation of life) which has been proven impossible in numerous laboratory experiments. It then depends upon random mutations, filtered by natural selection, to produce incredibly complex biological systems. This is simply wishful thinking, contrary to actual observations of how the natural world works.
The real reasons for believing the theory of evolution are rooted in religious and political agendas, not science. Science is against evolution.
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Mark Grabowski & William L. Jungers, Nature Communications 8, 12 October 2017, “Evidence of a chimpanzee-sized ancestor of humans but a gibbon-sized ancestor of apes”, https://www.nature.com/articles/s41467-017-00997-4