Ancient Footprints Show Human-Like Walking Began Nearly 4 Million Years Ago

[Geriatrix]

http://www.sciencedaily.com/releases/2011/07/110719194356.htm

Scientists at the University of Liverpool have found that ancient footprints in Laetoli, Tanzania, show that human-like features of the feet and gait existed almost two million years earlier than previously thought.

Many earlier studies have suggested that the characteristics of the human foot, such as the ability to push off the ground with the big toe, and a fully upright bipedal gait, emerged in early Homo, approximately 1.9 million years-ago.

Liverpool researchers, however, in collaboration with scientists at the University of Manchester and Bournemouth University, have now shown that footprints of a human ancestor dating back 3.7 million years ago, show features of the foot with more similarities to the gait of modern humans than with the type of bipedal walking used by chimpanzees, orangutans and gorillas.

The footprint site of Laetoli contains the earliest known trail made by human ancestors and includes 11 individual prints in good condition. Previous studies have been primarily based on single prints and have therefore been liable to misinterpreting artificial features, such as erosion and other environmental factors, as reflecting genuine features of the footprint. This has resulted in many years of debate over the exact characteristics of gait in early human ancestors.

The team used a new statistical technique, based on methods employed in functional brain imaging, to obtain a three-dimensional average of the 11 intact prints in the Laetoli trail. This was then compared to data from studies of footprint formation and under-foot pressures generated from walking in modern humans and other living great apes. Computer simulation was used to predict the footprints that would have been formed by different types of gaits in the likely printmaker, a species called Australopithecus afarensis.

Professor Robin Crompton, from the University of Liverpool's Institute of Ageing and Chronic Disease, said: "It was previously thought that Australopithecus afarensis walked in a crouched posture, and on the side of the foot, pushing off the ground with the middle part of the foot, as today's great apes do.

"We found, however, that the Laetoli prints represented a type of bipedal walking that was fully upright and driven by the front of the foot, particularly the big toe, much like humans today, and quite different to bipedal walking of chimpanzees and other apes.

"Quite remarkably, we found that some healthy humans produce footprints that are more like those of other apes than the Laetoli prints. The foot function represented by the prints is therefore most likely to be similar to patterns seen in modern-humans. This is important because the development of the features of human foot function helped our ancestors to expand further out of Africa.

"Our work demonstrates that many of these features evolved nearly four million years ago in a species that most consider to be partially tree-dwelling. These findings show support for a previous study at Liverpool that showed upright bipedal walking originally evolved in a tree-living ancestor of living great apes and humans. Australopithecus afarensis, however, was not modern in body proportions of the limbs and torso.

"The characteristic long-legged, short body form of the modern human allows us to walk and run great distances, even when carrying heavy loads. Australopithecus afarensis had the reverse physical build, short legs and a long body, which makes it probable that it could only walk or run effectively over short distances. We now need to determine when our ancestors first became able to walk or run over the very long distances that enabled humans to colonise the world."

Dr Bill Sellers, from the University of Manchester's Faculty of Life Sciences, said: "The shape of the human foot is probably one of the most obvious differences between us and our nearest living relatives, the great apes. The difference in foot function is thought to be linked to the fact that humans spend all of their time on the ground, but there has been a lot of debate as to when in the fossil record these changes occurred. Our work shows that there is considerably more functional overlap than previously expected.

"The Laetoli footprint trail is a snapshot of how early human ancestors used their feet 3.7 million years ago. By using a new technique for averaging footprints, foot pressure information from modern great apes, and computer simulation of walking in the proposed Laetoli printmaker, we can see that the evidence points to surprisingly modern foot function very early on in the human lineage."

The research, funded by the Leverhulme Trust and the Natural Environment Research Council (NERC), is published in the Royal Society journal Interface.

 

[porchrat]

Awesome!

 

[FuLL_MeT4L]

Guess-work! But still interesting.

 

[mfumbesi]

I was looking for a part where they explained how they dated the foot prints to 3.7million years.

 

[K3NS31]

I was looking for a part where they explained how they dated the foot prints to 3.7million years.

Probably used the layer of rock it was found in for an estimate, and radiometric dating for more precision.

 

[Ninja'd]

Many earlier studies have suggested that the characteristics of the human foot, such as the ability to push off the ground with the big toe, and a fully upright bipedal gait, emerged in early Homo, approximately 1.9 million years-ago.

The scientists should stop studying the footprints and start investigating how they built kitchen cupboards millions of years ago.

 

[General P]

How accurate and reliable are these calculations? Always when I hear something like this I'm reminded of the KBS-tuff problem which raises more questions than answers

 

[Pooky]

I'm always interested to know how they manage to date these things back so far, and I'm not sure how reliable it is.

 

[K3NS31]

I answered the "how do they get such accurate dates" question already. BEFORE you guys (General P and Pooky) posted.
Google "radiometric dating" and come back when you're done. Geez.

Edit, it's both reliable and accurate would be the short answer to your questions.

 

[HapticSimian]

I'm always interested to know how they manage to date these things back so far, and I'm not sure how reliable it is.

Are you truly interested, or are you just interested in posing all sceptical and controversial-like. If you are interested, the information is all out there... there's no big conspiracy.

 

[ponder]

Nonsense, the earth is only 6000 yrs old

 

[Palimino]

http://www.sciencedaily.com/releases/2011/07/110719194356.htm

Yeti? Big-foot?

 

[Palimino]

How accurate and reliable are these calculations?

Not very. They’re probably wrong by months. Maybe even a year or two. Unreliable dating.

 

[General P]

Edit, it's both reliable and accurate would be the short answer to your questions.

I don't think it's that simple. I’m not disputing the science behind radiometric dating, the big question is that is it practical? The KBS Tuff was radiometric dated to be 212-220 million years old in 1969. In the 1970’s Richard Leakey and his team found a human skull and other fossils that were too modern to be beneath Tuff (at the level they were found) and so the tuff was re-dated (using various radiometric dating methods) at 1.8-2.6 million years old. Now this is way down from 200 to 2 million. What worries me (and perhaps the big question) is that would anybody have questioned the date of the KBS Tuff if the fossils had not been found?

 

[HapticSimian]

I don't think it's that simple. I’m not disputing the science behind radiometric dating, the big question is that is it practical? The KBS Tuff was radiometric dated to be 212-220 million years old in 1969. In the 1970’s Richard Leakey and his team found a human skull and other fossils that were too modern to be beneath Tuff (at the level they were found) and so the tuff was re-dated (using various radiometric dating methods) at 1.8-2.6 million years old. Now this is way down from 200 to 2 million. What worries me (and perhaps the big question) is that would anybody have questioned the date of the KBS Tuff if the fossils had not been found?

1. 1969. Nineteen... Sixty... Nine...

2. Claim CD031

"The KBS Tuff controversy illustrates many of the problems with radiometric dating, but it equally illustrates that the problems are not insurmountable.

The KBS Tuff (for "Kay Behrensmeyer Site," after the geologist who first described it) is a layer of redeposited volcanic ash, so it contains a mixture of older sediments, too. It is still possible to date the layer, but care must be taken to choose only the youngest rocks, else one would be dating the age of older sediments washed into the layer, not the age of the layer itself. This is what happened with the first ages reported from the tuff. In a study to test the feasibility of dating samples from the tuff, the samples were contaminated with non-juvenile components which could not be separated out, giving ages over 200 million years. It was recommended that new samples be collected from which suitable individual crystals could be separated (Fitch and Miller 1970). These new samples were dated at 2.61 +/- 0.26 million years, based on the 40Ar/39Ar dating method (Fitch and Miller 1970).

Discrepancies with this date soon turned up, though. Work with animal fossils, particularly of pigs, showed that the strata in question matched younger strata in the nearby Omo Valley. In its early stages, this fossil work was imprecise enough that the 2.61 Myr date could still be justified (Maglio 1972). However, the fossils continued to point to a younger date as the quality of the work on them improved (White and Harris 1977). And in 1975, another lab, using K-Ar dating, reported dates of 1.82 and 1.60 Myr (Curtis et al. 1975).

Fitch and Miller turned to an independent method to resolve the discrepancy, fission-track dating. Initial results gave an age of 2.44 +/- 0.08 Myr (Hurford et al. 1976). This fit well with the age of 2.42 Myr, which Fitch et al. (1976) recalculated from their original results. Subsequent 40Ar/39Ar measurements they took gave a scattering of ages from 0.52 +/- 0.33 to 2.6 +/- 0.3 Myr. They attributed the spread to reheating of the crystals after deposition. Paleomagnetic studies gave ambiguous results (Brock and Isaac 1974; Hillhouse et al. 1977).

The weight of evidence soon began to converge on an age near 1.9 Myr, though. A study of trace elements in the minerals showed that the KBS Tuff correlates with the H2 tuff in the Shungura Formation, uncontroversially dated about 1.8 Myr (Cerling et al. 1979). The 1.60 Myr age reported by Curtis et al. (1975) was found to be an error due to a faulty balance (Drake et al. 1980). A later fission-track study which took pains to eliminate possible errors gave an age of 1.87 +/- 0.04 Myr (Gleadow 1980). Because the controversy had become quite heated, another expert, Ian McDougall, was called in to do independent dating. He came up with an age of 1.89 +/- 0.01 using K-Ar dating and 1.88 +/- 0.02 using 40Ar/39Ar dating (McDougall et al. 1980; McDougall 1981, 1985). Geological evidence and the consistency of dates derived from various sources indicates that reheating after deposition is unlikely.

The lessons to be learned from the KBS Tuff dating controversy are not that radiometric dating does not work, but that it works with some caveats.
Some formations are easier to date than others. The KBS Tuff was particularly difficult to date because it included volcanic sediments of several different ages. Furthermore, it looked the same as other tuffs, so care was needed to make sure the same layer was being referred to in different areas. All of this requires careful work from knowledgeable geologists. Were it not for its importance to determining the ages of important hominid fossils, geologists probably would not have bothered with dating it at all.
Some dating techniques are simply inappropriate in some circumstances. As noted above, paleomagnetic study is not particularly useful at this site.
Discrepant dates are not dismissed out of hand. In addition to trying to resolve the issue with further dating, the discrepancies caused people to look for the sources of error. The original erroneous date by Fitch and Miller could be an accurate date of a roughly 2.5 Myr ash layer, present in neighboring areas but apparently eroded from the Koobi Fora Formation. Apparently, some pumice from that volcanic event had been incorporated into the KBS Tuff. Samples sent to an independent lab for "blind" dating confirmed its older age (Fitch et al. 1996). Alternatively, this and other discrepant ages may be due to contamination with older material. Such contamination caused ages in the 2.0 - 6.2 Myr range in the analysis of Curtis et al. (1975) until they revised their sample purification procedures. A high atmospheric argon contamination in their samples and analytical errors may have contributed, too (McDougall et al. 1980).

The fission-track study which gave the 2.44 Myr age was the first such study to date zircons so young. The reanalysis by Gleadow (1980) noted problems with the standard methods and contributed new methodology for dealing with zircons with low track densities.
People's preconceptions and personalities can get in the way of evaluating the data objectively. In the KBS Tuff controversy, personality conflicts may have contributed to delay in the resolution and certainly contributed to the drama. But in the end, the objective evidence is a constraint that every scientist must meet. Replication, free access to information, and awareness of conflicts of interest help assure that personal foibles do not determine outcomes. Because such mechanisms were in place, all of the scientists who initially supported the older 2.6 Myr date for the KBS Tuff later came to accept the 1.88 Myr age (Lewin 1987).

Note that different methods give the same results when known sources of error are removed. K-Ar, 40Ar/39Ar, and fission-track methods ultimately all gave the same results. These results were correlated with strata of the same age at other locations on the basis of fossil and trace element analysis.

The different ages which were seriously debated for the KBS Tuff, from 1.6 to 2.6 million years, were never close to ages required by young-earth creationism.

 

[K3NS31]

1. 1969. Nineteen... Sixty... Nine...

2. Claim CD031

Thanks, very interesting.

 

[General P]

I have seen this article (http://www.talkorigins.org/indexcc/CD/CD031.html) before and I understand how we got the new date. What triggered the re-calculation was really the discovery of the fossils. In the article itself the guy admits this, watch what he says;

"Work with animal fossils, particularly of pigs, showed that the strata in question matched younger strata in the nearby Omo Valley."

"However, the fossils continued to point to a younger date as the quality of the work on them improved (White and Harris 1977)."

The other result;

"Subsequent 40Ar/39Ar measurements they took gave a scattering of ages from 0.52 +/- 0.33 to 2.6 +/- 0.3 Myr."

The lower bracket is 1.6 my but this calculation shows 0.52 +/- 0.33. I can't help but wander if this result discarded based on the average of all calculations or on the fossils?

So we do know why the first date of the Tuff was wrong. Can we then absolutely and safely say that other dates of different locations are reliable & accurate?

I am teachable but radiometric dating is just not convincing enough for me, there is just too much room huge errors here.

 

[K3NS31]

I have seen this article (http://www.talkorigins.org/indexcc/CD/CD031.html) before and I understand how we got the new date. What triggered the re-calculation was really the discovery of the fossils. In the article itself the guy admits this, watch what he says;




The other result;

The lower bracket is 1.6 my but this calculation shows 0.52 +/- 0.33. I can't help but wander if this result discarded based on the average of all calculations or on the fossils?

So we do know why the first date of the Tuff was wrong. Can we then absolutely and safely say that other dates of different locations are reliable & accurate?

I am teachable but radiometric dating is just not convincing enough for me, there is just too much room huge errors here.

I suggest you start a new thread and ask about this. There are many people on the forum who are knowledgeable and explain well. They won't see your question buried here though. Especially as it's off topic.

 

[Pooky]

Are you truly interested, or are you just interested in posing all sceptical and controversial-like. If you are interested, the information is all out there... there's no big conspiracy.

I am interested in this but I think I need to do somescience studies or something cause the information on wikipedia just flies past my head!

 

[Pooky]

How were these footprints captured? Were they like cement moulds or something?