Transitional forms in human evolution

Faith & Science Conversation
106

It’s not rocket science, so to speak. There is the colloquial usage of “human,” and there is the scientific usage. The ordinary usage refers to “us” (H. sapiens) in distinction from other living creatures, while the scientific usage includes other extinct hominins (any member of the Homo genus) under the umbrella term “human.” (Some anthropologists want to throw “Lucy” into the mix, but I have no dog in that hunt.)

In ordinary usage, it is perfectly acceptable to make a distinction such as “a human infant and Neanderthal infant.” No one is confused by the meaning of “human” in that sentence. In a scientific paper, one would say “sapiens infant and Neanderthal infant” to be more specific, since H. neanderthalensis is a member of our genus and also “human” in scientific parlance.

We don’t need new definitions of “human.” We just have to be aware of the context. Most non-scientists are just confused when you start referring to heidelbergensis or erectus as human.

No, this is called LUCK. Most species that have existed on this planet are now extinct. Do you really expect that scientists would have found an example of every single one of them?

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107

You make my point well. A variable definition subject to confusion, especially in scientific news articles aimed at lay audiences.

108

Yes you’re quite right about Homo/Human. Then add Hominid for any member of the group consisting of all modern and extinct humans and great apes (including gorillas, chimpanzees, and orangutans) and all their immediate ancestors. It makes it sound as if there is scientific proof that Homo and apes evolved from a common ancestor.

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You don’t need any fossils at all for that proof, it’s all in the genes. Same way you can tell who a baby’s father or cousin is, when geneticists compare our DNA to apes’, they can tell we’re related. Fossils are just icing on the cake.

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110

Hi Chris,

You’re using the wrong word – “proof” – with regard to science. There is very strong evidence, strong evidence, suggestive evidence, and even disproving evidence, but no such thing as proof.

With regard to the question we are discussing, you make it sound as if you have not read key peer-reviewed research papers in the field. Thus I present to you the following:

Analyzing Hominin Hominin Phylogeny: Cladistic Approach
This is a review of the literature as of 2015

Phylogenetic signal of genomic repeat abundances can be distorted by random homoplasy: a case study from hominid primates
This peer-reviewed article presents a detailed methodology of a hominid phylogenetic research project. It includes downloadable data, open-source software, methodology, and even a Github repository for Python scripts.

If you think, @aarceng, that the research team made a mistake that was not caught by the peer reviewers, you can reproduce the research yourself using their data, tools, and Python scripts, show where they went wrong, and publish an improved analysis.

@glipsnort may have a suggestion or two regarding key peer-reviewed research that establishes the hominid phylogeny. Got any links for us, Steve?

@aarceng - I hope you have fun while learning from these resources I found for you. I certainly had educational fun as I looked through them.

Best,
Chris

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111

What is meant by “ the big toe, while slightly divergent from the other four digits” can seen from the picture in the ref which shows feet not easily distinguished from humans.
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This shows that the article and reconstruction are out of date since it is now well accepted that Australopiths had a splayed and short big toe just like modern apes. Which you can see in Little Foot and also in a more recent construction of a Lucy model by paleoartist Johm Gurch.
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The ref article talks about the Laetoli Tracks which at the time were speculated to have been made by Australopiths. Since this is ruled out by more accurate Australopith feet shape shown that leaves only one creature that is known to make footprints that match the Laetoli Tracks.

tbc/… (sorry, out of time atm)

112

Hi Chris,

Paleoartists typically do excellent work that helps the public understand the findings of paleontologists and paleoanthropologists. That said, their work is not peer-reviewed…

From the same article @Lynn_Munter cited and you are inclined to refute, I present a Laetoli cast:

https://milnepublishing.geneseo.edu/the-history-of-our-tribe-hominini/wp-content/uploads/sites/6/2016/12/image13-200x300.jpg

This seems to be roughly intermediate between the foot shape of non-Homo hominids and the foot shapes found in genus Homo.

Not sure what you’re referring to here.

Best,
Chris

113

Chris, good of you to try to jump in with a rescue device but in doing so you have just agreed that the article Lynn quotes is wrong regarding the shape of the Australopith foot. But you’re wrong too. The cast of print from the Laetoli track still doesn’t match what would be left by an Australopith foot. Remember that a footprint will not be an exact replica of the foot that formed it since the foot goes through a range of motion and pressure distributions while making the print. Even on a sandy beach with “just right” moisture content you don’t get a perfect match. The prints have been examined by experts who agree that they match Human footprints. So you could argue that they are made by H.erectus or another H. but definitely not by A. afarensis.

114

Could you cite some links, please? I have seen human footprints–I have visited beaches many times. Human footprints seem quite different from the Laetoli prints, in my opinion.

Best,
Chris

115

I think a footnote is in order here, which experts?

A couple of relevant papers:

Laetoli footprints reveal bipedal gait biomechanics different from those of modern humans and chimpanzees

Laetoli Footprints Preserve Earliest Direct Evidence of Human-Like Bipedal Biomechanics

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116

I think this is the opposite of the truth.

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117

You seem to have misunderstood the research. The Laetoli prints were produced by bipedal hominins with a gait similar to humans’. However, the bone structure and dating do not support the claim that they were made by members of the genus Homo. From Ron Sewell’s second link:

These results provide us with the earliest direct evidence of kinematically human-like bipedalism currently known, and show that extended limb bipedalism evolved long before the appearance of the genus Homo . Since extended-limb bipedalism is more energetically economical than ape-like bipedalism, energy expenditure was likely an important selection pressure on hominin bipeds by 3.6 Ma.

Best,
Chris

118

@rsewell @sfmatheson @Chris_Falter

Which experts?

However before very long these four prints were entirely eclipsed by the discovery undoubted human footprints, some of which were of the greatest clarity.

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Mary Leaky, Disclosing the Past,p176

At Laetoli, Tanzania, some hominins walked across a bed of wet volcanic ash 3.6 million years ago. “When I saw those footprints being excavated, I thought, gosh, you’d lose these on a modern day beach, they have an arch and a totally human gait,” recalls Latimer. However, the movements were so close to human that many palaeontologists doubted they could have possibly belonged to the ancient A. afarensis.
Bruce Latimer

On the other hand, when we compare the Laetoli print to that of a crime scene human print, they’re virtually indistinguishable. The great toe is in line with the rest of the toes. And what this has done in the human and the Laetoli print is to create an arch. And that’s a hallmark of typical modern upright locomotion, because the arch is an energy absorber.
Owen Lovejoy

Using an experimental design, we show that the Laetoli hominins walked with weight transfer most similar to the economical extended limb bipedalism of humans. Humans walked through a sand trackway using both extended limb bipedalism, and more flexed limb bipedalism. Footprint morphology from extended limb trials matches weight distribution patterns found in the Laetoli footprints.
Raichlen DA et al.

I note that Raichlen goes on to say " These results provide us with the earliest direct evidence of kinematically human-like bipedalism currently known, and show that extended limb bipedalism evolved long before the appearance of the genus Homo ." However that incorporates the assumption that humans had not developed yet.

Thank you Ron for the links you provided. I have included one above. Having read the other paper by Kevin G. Hatala et. al., I think I would wait for more comment before I accept those results. Just looking at the photos in Fig 1 you can see that the Laetoli prints closely match humans taking into account the somewhat degraded nature of the fossil prints. They are clearly not chimp and also not A. afarensis based on the reconstructions I posted above.

Unless you make the assumption, as Raichlen does, that no Homo were around the best conclusion is the Laetoli prints were made by a Human with very modern feet and gait, possibly H. erectus or even H. sapiens.

119

I looked at your first citation and this is a case in point of why I don’t trust anything YECs cite ever. You left out the key sentence where Latimer says the sentence you are trying to use as a quote mine about experts doubting that the footprints are A. afarensis is a moot point now.

“When I saw those footprints being excavated, I thought, gosh, you’d lose these on a modern day beach, they have an arch and a totally human gait,” recalls Latimer. However, the movements were so close to human that many palaeontologists doubted they could have possibly belonged to the ancient A. afarensis. “This work certainly puts a nail in the coffin of that argument,” says Latimer.

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120

This quote mine is just as bad. The entire conversation is in the context of transitional forms from ape to human; it isn’t about whether the footprints were not made by A. afarensis and were made by Homo instead. The line after this paragraph, the host responds, “So a picture of Lucy and her kind begins to emerge.” Lucy and her kind are A. afarensis. Plus, it’s a TV show, not a peer reviewed journal.

Then you admit that your third quote source doesn’t really prove your point, but that’s just because of his unbiblical assumptions that humans had not developed in the time period the footprints were dated.

So basically, you got nothing here.

Now my question is, did you not understand that these experts don’t support what you are claiming at all, or did you realize it, but just hope no one would read the sources for themselves? Do you understand why many of us feel like YEC advocates are intentionally deceptive in the way they present their “evidence?”

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121

In a separate thread here on the forum, a few of us have been discussing how and why Christians deconvert. The behavior shown here is a relevant data point.

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122

You’d think a righteous position would entail honesty and integrity. I doubt if God would welcome any dirty tricks operation on His behalf.

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123

Depends on the god. One of the popular ones commanded genocide and slavery.

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124

Those who insist on inerrancy or literalism may be troubled by these issues but I suspect there are good hermeneutical pathways through such difficulties for those determined to find them. Personally though, I don’t believe there was ever a time when the nature of God was laid bare for all to see. Apparently the only way around the hiddenness of God is the belief that God Himself reached through the natural/supernatural membrane to deliver the only official message He deemed necessary. If you believe He established his bonafides at that time and are not bothered that He wouldn’t do more to maintain that same level of transparency on an ongoing basis … then the church and the bible may be the path for you.

Luckily my concept of God owes little to the Bible beyond suggesting the existence of a wise Other who cares about me and others who is intimately aware of my struggles. Having grown up spiritually feral that is the only role for God I feel obliged to defend. To my mind it is a mistake to insist that God must be behind all creation and infinitely powerful. That just makes God seem incompetent whereas I see God as doing His best as an inner counselor. Perhaps He is more than that, but perhaps not.

125

Jesus said “if you’ve seen me, you’ve seen the Father.” Pretty audacious claim to be sure. If one is a Christ follower, one reads the OT through the lens of Jesus being the clearest demonstration of what God is like. God is the shepherd that looks for the one, leaving the 99. He’s the God who scandalously runs to embrace the prodigal son. And so on.

Yes, many times folks who claim to follow this Jesus person don’t seem to see things the same way as he did. I get that.

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