Footprints in Ancient Ash

Scientists are pretty sure that Saccorhytus coronarius is an ancestor of lancets, sea squirts, fish, amphibians, reptiles, dinosaurs, and mammals: including us.

Much more recently, about 3,660,000 years back, five Australopithecus afarensis strolled across volcanic ash. One of them was “astonishingly larger” than any other A. afarensis we know of. Exactly what that means isn’t, I think, clear. Not yet.

  1. Tiny Critter, Big Mouth; and an Early Ancestor
  2. Footprints

Humility, Catholic Style

Humility, the Catholic version, is accepting reality and acknowledging that God’s God.

HUMILITY: The virtue by which a Christian acknowledges that God is the author of all good. Humility avoids inordinate ambition or pride, and provides the foundation for turning to God in prayer (2559). Voluntary humility can be described as ‘poverty of spirit’ (2546).”
(Catechism of the Catholic Church, Glossary)

I’ve talked about humility, hubris, and getting a grip, before. (August 28, 2016; August 26, 2016; July 31, 2016)

Rejecting reality, avoiding truth, isn’t an option for me. Not if I take my faith seriously.

Faith, the Catholic version, is a willing and conscious “assent to the whole truth that God has revealed.” (Catechism, 142150)

Truth, whether it’s expressed in words, “the rational expression of the knowledge of created and uncreated reality;” or “the order and harmony of the cosmos;” or in other ways — is important, and beautiful. (Catechism, Prologue, 27, 74, 2500, 2505, more under Truth in the index)

Noticing God’s infinite beauty reflected in “the world’s order and beauty” tells us a little about God. Again, if we’re paying attention. (Catechism, 3132, 341)

A thirst for truth and happiness is written into each of us. If we’re doing our job right, it’ll lead us to God. (Catechism, 27)

I went over this last month, and almost certainly will again. (January 13, 2017)

Reality and Faith

There are some odd notions about faith and reason, science and religion, floating around. But I’m a Catholic, so using my brain is okay. It’s a requirement, actually. (Catechism, 154, 159, 1951, 1778, 2293)

I’ve said that before, too. Often. (December 23, 2016; December 9, 2016; October 5, 2016; August 28, 2016)

Basically, I think accepting reality makes sense: even if — particularly if — that means learning something new.


1. Tiny Critter, Big Mouth; and an Early Ancestor


(From Cambridge University, via BBC News, used w/o permission.)
(“Artist’s reconstruction of Saccorhytus coronarius, based on the original fossil finds. The actual creature was probably no more than a millimetre in size”
(BBC News))

(From Jian Han et al., via Nature, used w/o permission.)
(“Reconstruction of Saccorhytus coronarius … Lateral, hind and ventral views….”
(Jian Han et al., via Nature))

Scientists find ‘oldest human ancestor’
Pallab Ghosh, BBC News (January 30, 2017)

Researchers have discovered the earliest known ancestor of humans – along with a vast range of other species.

“They say that fossilised traces of the 540-million-year-old creature are ‘exquisitely well preserved’.

“The microscopic sea animal is the earliest known step on the evolutionary path that led to fish and – eventually – to humans….”

Saccorhytus coronarius lived about 540,000,000 million years back, during the early Cambrian explosion. That was when most phyla we have today showed up.

A phylum is the taxonomic rank below kingdom and above class. Phyla can be define by genetic or body plan similarities, thinking of plants having a body plan seems odd, and that’s another topic.

“Taxonomy” is a five-dollar word for the habit we have of sorting critters into categories: like plant, animal, or fungus. We’ve probably been doing that since day one, but the current systems go back to Carl Linnaeus.

I’ve talked about taxonomy and what we’ve been learning since my high school years before. (September 23, 2016)

Artist’s reconstructions like the one in the BBC News piece help folks ‘see’ what scientists are talking about, but necessarily involve a little imagination. I doubt that we can be sure about the colors, for example.

On the other hand, these fossils really were remarkably well-preserved.

Identifying Parts


(From Jian Han et al., via Nature, used w/o permission.)
(“Saccorhytus was also covered with a thin, relatively flexible skin and muscles. It probably moved around by wriggling”
(BBC News))

(From Jian Han, Northwest University, China; via BBC News, used w/o permission.)
(“Saccorhytus coronarius gen. et sp. nov. from the Cambrian Kuanchuanpu Formation, South China….”
(Jian Han et al., via Nature))

This is what the scientists had to work with. As I said, the level of detail is impressive, particularly since the critters were only about a millimeter across.

Jian Han and the rest are reasonably sure that the feature marked “M” is a mouth, and they’re pretty sure there weren’t any eyes.

Features other than the mouth almost certainly had some function, but exactly what they did is still a mystery. For now, they’re mostly labeled by what they look like.

Lbc1 through Lbc4 and Lbc1 through Lbc4 are the left (L) and right (R) body cones one through four, for example.

Now, about these critters being the “earliest known ancestor of humans.”

Saccorhytus coronarius is the the earliest-known deuterostome, a broad category of animals that have the same general pattern of embryonic development. Some scientists call it a superphylum, since it includes three phyla.1

Life on Earth has changed, a lot, over the last half-billion years, and that’s yet another topic.


2. Footprints


(From Dawid A. Iurino, via BBC News, used w/o permission.)
(“The footprints may have been made by a male walking with smaller females and juveniles”
(BBC News))

Fossil footprints tell story of human origins
Helen Briggs, BBC News (December 14, 2016)

Footprints made by early humans millions of years ago have been uncovered in Tanzania close to where similar tracks were found in the 1970s.

“The impressions were made when some of our distant relatives walked together across wet volcanic ash.

“Their makers, most likely Australopithecus afarensis, appear to have had a wide range of body sizes.

“Scientists say this gives clues to how this ancient species of human lived….”

Australopithecus afarensis lived in east Africa between 3,900,000 and 2,900,000 years ago. I’m not sure whether they’re a ‘what’ or a ‘who,’ but I’m guessing it’s ‘who.’

Lucy,” our name for a now-famous A. afarensis skeleton, was about 1.1 meters (3 feet 7 inches), tall and weighed around 29 kilograms (64 pounds).

That’s short by today’s standards, even in places like Bolivia and Indonesia, where women average 1.42 meters (4 feet 8 inches) and 1.47, meters (4 feet 10 inches).

I talked about Lucy and A. afarensis last year. (September 23, 2016)

What’s “average” depends on who you listen to, and where you are. I grew up among Norwegian- and German-Americans, so although I’m about “average” height for man, globally, I still think of myself as “short,” and that’s yet again another topic.

Anyway, the Australopithecus afarensis model was much shorter than today’s. They had slightly longer arms, for their height, than we do; and were probably a bit better at climbing trees. They walked like we do, though. The big differences were above the neck.

A. afaransis had room for about 380 to 430 cubic centimeters of brain. Today’s model, the European version at least, runs from about 975 to 1499 cubic centimeters.

Size isn’t everything, but my guess is that most if not all A. afarensis would have had a terrible time trying to pass their ACT or SAT: or blending into a crowd.

Tools and People

That doesn’t, I think, make them not-people.

The earliest stone tools we’ve found are about 3,300,000 years old and were in the same area.

Quite a few animals use tools, but it’s likely that A. afarensis made these.

They’re not up to the standards I’d expect to see in a Home Depot; but upwards of three million years later, I’d hope that we’d made some improvements.

Oldowan tools, like those choppers, came along later, about 600,000 years after Lucy’s day.

They were a leading technology in east Africa from around 2,600,000 to 1,700,000 years ago, before folks invented Acheulean tools in east and southern Africa

Oldowan tools were still in use a hundred thousand years after that, where northern China is today.

But the new tech eventually caught on, showing up in today’s France and China.

Oldowan choppers are like a hatchet without a handle.

They’re good for — well, for chopping — food, wood, or other softish materials.

An equivalent kitchen item is today’s mezzaluna. Obviously, the design has changed a bit over the last few million years.

I think it’s likely that “Lucy” was “human” in the sense of being a person.

It’s not just tool use or walking upright.

We’ve learned that ArhGAP11B, a gene that’s unique to humans, showed up roughly 5,000,000 years back. The gene affects brain size: particularly the neocortex.

Another uniquely-human ‘brain gene,’ SRGAP2, showed up later. (January 13, 2017; September 23, 2016)

Between making tools, looking a bit like us, and being around long after a uniquely-human gene appeared: yeah, I’m willing to think that “Lucy” may have been a person.2

“Astonishingly Larger”


(From Raffaella Pellizzon, via BBC News, used w/o permission.)
(The footprints were made in volcanic ash about 3,660,000 years ago)

“…The newly discovered footprints may have been made by a male walking with smaller females.

“‘This novel evidence, taken as a whole with the previous findings, portrays several early hominins moving as a group through the landscape following a volcanic eruption and subsequent rainfall. But there is more,’ said lead researcher Prof Giorgio Manzi, director of the archaeological project in Tanzania.

“‘The footprints of one of the new individuals are astonishingly larger than anyone else’s in the group, suggesting that he was a large male member of the species.

“‘In fact, the 165cm stature indicated by his footprints makes him the largest Australopithecus specimen identified to date.’…”
(Helen Briggs, BBC News)

“…A possible tentative conclusion is that the various individuals represented at Laetoli are: S1, a male; G2 and S2, females; G1 and G3, smaller females or juvenile individuals….”
(Fidelis T Masao et al, eLife3)

165 centimeters, 1.65 meters, 5 feet 5 inches, is taller than some men in my extended family. Either that individual was really tall by then-contemporary standards, or our sampling of A. afarensis is skewed: which is far from impossible.

We haven’t found all that many examples of A. afarensis.

Not all critters, people included, become fossils. I’m not convinced that our preferred habitats favor fossilization.

The habit of burying our dead might or might not help, particularly since that’s not the only option we’ve developed for dealing with death, and that’s still another topic. Topics. (November 11, 2016; September 23, 2016)

I’m reasonably sure that the five individuals were about as tall as the scientists say they were. We’ve learned a great deal about how critters, people included, move since Aristotle realized that animals can be viewed as mechanical systems.3

Analysis, Sexual Dimorphism, and Dignity

The size, depth, and spacing of the footprints tell us a lot: including how big the folks were, and how fast they were moving. In this case, they were all walking; slowly. The scientists got speeds of about 0.44 to 0.9 meters per second, depending on which analysis method they used.

That sort of analysis I’m pretty confident about.

Whether we’re looking at a family group that’s organized along ‘gorilla’ lines or not: that, I’m not so sure about.

We may learn that the Laetoli footprints were made by a good 50th percentile sample of the A. afarensis population. If they are, that model’s sexual dimorphism was probably a lot greater than today’s.

Sexual dimorphism is the (average) difference between males and females in a species.

Like most, but not all, primates, human males are bigger than females. My side of humanity, for example, is on average 15% heavier than my wife’s, and a bit taller.

That’s on average, of course. Humans aren’t particularly dimorphic, so I’ve known quite a few women who are taller than I am, and men who are around my wife’s height.

Screwball politics of the last few decades being what they are, I’d better say that I don’t think I’m better than folks who are shorter than I am. But I also think pretending that women and men are identical, apart from cultural conditioning, is daft.

We have equal dignity, and that’s — what else? — another topic. (Genesis 1:27; Catechism, 2334)

Assumptions

Getting back to the Laetoli footprints, assuming that those five individuals were all part of the same family seems reasonable.

Assuming they were typical of all A. afarensis, not so much. But maybe they were. That’s something that’ll be easier to figure out when we have more data.

For now, just looking at the footprints, we could be looking at all individuals in one family; where the father is much taller than the wife/wives and kids. That doesn’t make the family structure gorilla-like.

They could have been a family not unlike mine; where the son is the tallest, followed in descending order by the father, some of the kids, the mother, and another one of the kids.

Or they could be the mothers and kids from two or more families, being escorted across an ash field by “Tiny.” The other menfolk might figure they could trust Tiny to deal with any dangers along the way, and that their wives would keep him in line.

Besides, if they were scouting out a good place to stop for the night, the outsize one of their number might not have been a good choice for a ‘stealth’ mission.

I’ll grant that having a mostly-Irish father and five-foot-nothing black-haired ekte norsk mother gives me a particular viewpoint.

I’m quite sure there are other possible ways to look at the data: and that scientists will be discussing them.

Had enough? If not, there’s more:


1 More than you need, and possibly want, to know about:

2 Australopithecus afarensis, ‘brain genes,’ and humanity’s past:

3 Footprints and using our brains:

About Brian H. Gill

I’m a sixty-something married guy with six kids, four surviving, in a small central Minnesota town. I mostly write and make digital art. I’m only interested in three things: that which exists within the universe; that which exists beyond; and that which might exist.

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