The Human Fossil Record, Part 2: Bipedality

Bookmark and Share

January 5, 2011 Tags: Human Origins

Today's entry was written by James Kidder. Please note the views expressed here are those of the author, not necessarily of The BioLogos Foundation. You can read more about what we believe here.

This is the second part of a series by James Kidder on the human fossil record. The first part can be found here.

One of the most fruitful and exciting areas of research in palaeoanthropology is the search for the last common ancestor to the higher apes and humans. This question is inextricably tied to concepts of what separates humanity from the animals around us. This is a question that has spiritual as well as physical ramifications. In this set of posts, we are dealing with what makes us human from a biophysical perspective.

Traditionally, paleoanthropologists have considered the hallmark of humanity to be habitual bipedalism. While we share many characteristics in common with the higher apes, this trait alone is practiced by no other animal. Some animals practice facultative bipedalism, allowing them to go short distances on two legs when necessary, but only humans use it as their only form of locomotion. Put a man on all fours and even a squirrel can outrun him. Bipedalism is a skill that we learn early in life, before we are sentient and even understand what makes us different from the animals around us. It is programmed into us.

Bipedalism is marked by a number of anatomical modifications to the standard primate body. These center on the pelvis and involve changes in the head (cranium) and the rest of the body (postcranium), reflecting a shifting of the center of balance from the abdominal cavity to the hip. In mammals, the hip is composed of three mirrored sets of bones: the ilium, the ischium and the pubis (Figure 1). The top part of the leg fits into the bottom-rear portion of the ilium, into a round socket called the acetabulum. It is one of two ball-and-socket joints in the body, the other being where the arm fits into the scapula at the top of your shoulder.

Where the two pubis bones fit together in the front and the two ilia meet in the back with the sacrum forms the birth canal. In chimpanzees and gorillas, the ilium is narrow and tall (Figure 2). Consequently, the connection to the upper leg bone, the femur, is straight up and down. In humans, the ilium is flat and flared, creating an outward bowing of the top of the femur, which allows for the balance necessary for walking upright (see Figure 1). This, in turn, creates what is known as the valgus knee, where the bottom of the femur meets the top of the large lower leg bone, the tibia, at an angle. The fact that the two bones meet at an angle provides for a better balance of the body mass for upright walking. In contrast, when higher apes such as gorillas and chimpanzees stand, the femur and the tibia are both perpendicular to the ground, resulting in a straight knee joint. Consequently, when chimpanzees walk upright, they swing side to side in an ungainly fashion to simulate the balance that is inherent in human walking.

Other changes are present above the hip, as well. Because they are quadrupedal, chimpanzees, gorillas and orangutans have a straight backbone, or vertebral column (Figure 3). In humans, the vertebral column resembles a double “s” shape, which balances the torso above the hip (and creates the back problems we suffer later in life). At the top of the spinal column, the top vertebra, the atlas, has facets that balance the head and the second vertebra, the axis, has a prong that fits directly into a hole in the skull. This hole, which is called the foramen magnum, is at the back of the skull in higher apes, as in all quadrupedal animals. This allows the animal to keep its head up while it is trotting along the ground. In humans, the foramen magnum is at the base of the skull, allowing us to look forward as we walk. It also makes it hard to look forward when we crawl on all fours. Each of these modifications is diagnostic of humans and easily recognizable in the fossil record in specimens for which these anatomical areas are present.

Ardipithecus ramidus and the Origins of Bipedality

The origins of bipedality have traditionally been understood as having evolved at the end of the Miocene epoch, around 6 to 8 million years ago (Crompton, Sellers and Thorpe 2010) when the climate began to dry out and cool. Unfortunately, there are only scattered presumed hominin remains from this time period, all of which are taxonomically controversial and fragmentary and none of which have diagnostic postcranial remains. It has also been thought that the transition to bipedality likely did not happen all at once but in mosaic fashion (as evolution often proceeds) and this has recently supported by the fossil record. Up until a few years ago, the most widely-accepted model was that bipedality originated among a group of large-bodied hominoids that had adapted to the savannah-jungle fringe. The jungle, itself, was ceded to the precursors of the modern chimpanzees and gorillas and the savannah to the precursors of the modern baboons and other terrestrial monkeys. As a result, some workers (Crompton et al. 2010) suggested that both arboreal (tree-dwelling) and terrestrial locomotion might have been present in our earliest ancestors. Recent evidence has corroborated some parts of this model, but not others.

In 1994, the remains of a remarkable hominin, dated to 4.4 million years ago, were unearthed in the Afar Triangle of Northeastern Ethiopia. Examination of the surrounding deposits, however, yielded a conclusion that this hominin lived in a woodland environment, rather than a savannah/forest fringe environment (White et al. 2009a). Requiring over ten years of extrication from the surrounding rock and painstaking reconstruction, this fossil form, Ardipithecus ramidus (now represented by 110 individuals) yields diagnostic parts of the pelvis (Figure 4), as well as sections of the arms and skull (Figure 5) (White et al. 2009b). Although the base of the skull is not preserved, one striking aspect of humanity is present in the teeth. The canine (eye tooth) does not extend beyond the tooth row. Humans are the only hominins for which this is the case. In all other ape species, fossil and extant, the canine projects well beyond the tooth row.

Biomechanics specialist Owen Lovejoy and colleagues (Lovejoy et al. 2009) write about this species:

“The gluteal muscles had been repositioned so that Ar. Ramidus could walk without shifting its center of mass from side to side. This is made clear not only by the shape of its ilium, but by the appearance of a special growth site unique to hominids among all primates (the anterior inferior iliac spine). However, its lower pelvis was still almost entirely ape-like, presumably because it still had massive hindlimb muscles for active climbing.”

Figure 6 shows the intermediate nature of the pelvis of Ardipithecus ramidus compared to later hominins (Homo sapiens, Au. Afarensis) and chimpanzees (P. troglodytes).

Ardipithecus, then, represents a shift away from the primitive locomotion employed by the last common ancestor of our line and that of modern chimpanzees. Here is a hominin that maintained a link with its tree-dwelling past and yet had progressed toward the bipedal future. This evidence is striking because it firmly demonstrates that a species had arisen that was advanced in the human direction. Whether or not it led to the hominin forms that followed is not known but it clearly represents a phenomenal example of a transitional form in the human fossil record.

From this point on, the forms become noticeably more human in appearance, leading eventually our own species some four million years later. In his infinite wisdom, God had set us on a path toward our eventual communion with Him. That this path took such a long period of time and through so many varied forms of humanity is a testament to His creative power and patience.

Next, the successors to Ardipithecus and true human walking.

Sources

Crompton, R., W. Sellers & S. Thorpe (2010) Arboreality, terrestriality and bipedalism. Philosophical Transactions of the Royal Society B: Biological Sciences, 365, 3301.

Lovejoy, C. O., G. Suwa, L. Spurlock, B. Asfaw & T. D. White (2009) The Pelvis and Femur of Ardipithecus ramidus: The Emergence of Upright Walking. Science, 326, 71, 71e1-71e6.

White, T. D., S. H. Ambrose, G. Suwa, D. F. Su, D. DeGusta, R. L. Bernor, J.-R. Boisserie, M. Brunet, E. Delson, S. Frost, N. Garcia, I. X. Giaourtsakis, Y. Haile-Selassie, F. C. Howell, T. Lehmann, A. Likius, C. Pehlevan, H. Saegusa, G. Semprebon, M. Teaford & E. Vrba (2009a) Macrovertebrate Paleontology and the Pliocene Habitat of Ardipithecus ramidus. Science, 326, 67, 87-93.

White, T. D., B. Asfaw, Y. Beyene, Y. Haile-Selassie, C. O. Lovejoy, G. Suwa & G. WoldeGabriel (2009b) Ardipithecus ramidus and the Paleobiology of Early Hominids. Science, 326, 64, 75-86.

Figure 1: http://www.bikemonkey.net/2010/01/3-series-tune-up-checking-the-pelvic-girdle/

Figure 2: http://www.boneclones.com/KO-303-P.htm

Figure 3: http://www.fixscoliosis.com/entries/13-The-Human-Spine-and-Idiopathic-Scoliosis

Figure 4: Bone Clones

Figure 5: National Geographic Images

Figure 6: from Lovejoy et al. 2009


James Kidder holds a Ph.D. in Biological Anthropology from the University of Tennessee (UT). He currently employed as an instructor at UT, and as a science research librarian at Oak Ridge National Laboratory. He has been involved in the Veritas Forum at UT and runs the blog "Science and Religion: A View from an Evolutionary Creationist/Theistic Evolutionist."

< Previous post in series Next post in series >


View the archived discussion of this post

This article is now closed for new comments. The archived comments are shown below.

Loading...
Page 9 of 12   « 6 7 8 9 10 11 12 »
Rich - #47606

January 16th 2011

Martin (continued from 47603):

Martin, either you were raised as a Christian, or you became a Christian later in life.  If you were raised as a Christian, I am betting that your parents, ministers, elders, etc. pointed you to the Bible and said something like:  “This is the Word of God.  It is inerrant.  It tells the truth, the whole truth, and nothing but the truth.”  I doubt they said to you:  “This is a collection of ancient Israelite writings which, many of us believe, has some important wisdom to guide you in life.  Some say that it contains errors and contradictions.  Perhaps this is so, but we still think it is true in the main, and we recommend that you read it with an open mind.”

And if you were converted to Christianity, I doubt the evangelicals who converted you said:  “This is the Bible.  I believe it contains the inerrant word of God.  I decided this after learning Greek and Hebrew, then carefully and critically studying it for 10 years, comparing the opinions of the various authors, and deciding based on my own reasoning that the authors were in total agreement.  I recommend that you do the same, and that—if 10 years from now you agree with me—you become a Christian.”

(continued)


Jimpithecus - #47609

January 16th 2011

Sorry, I was off the grid for a couple of days.  Marriage Retreat.  Nebrek writes:

“What do you believe is the greatest evidence against recent creation of the Earth, and a world wide flood?”

Where to start.  For one, all of astrophysics and astronomy converges on a universe creation date of around 13-14 billion years ago.  We know that light travels 168 k miles per second.  Since this is the case, light from these stars must have taken, in some cases, many millions of years to reach us.  Star light red shift patterns clearly show that for some objects out in the heavens, light has been traveling in excess of five billion years.  Radioactive elements such as uranium have half-lives of several billion years and some elements with longer half-lives don’t exist anymore but we know, based on the decay products they leave behind that they once did.

—next—


Jimpithecus - #47610

January 16th 2011

Every independent radiometric dating technique that has been used, including the isochron methods, reveals a terrestrial creation of 4.5 billion years ago.  Why are they all so exact if they use different elements?  Here is an excellent article by Chris Stassen that goes into greater detail than I have


For the world-wide flood, the contra-evidence is huge.  I finished not too long ago, a book by Davis Young on how the church explained the geological evidence as it rolled in and that is very instructive.  I am only touching the surface here okay.

If one reads the accounts of Henry Morris and John Whitcomb and the various articles that have been written since, they all argue for a flood that was turbulent, with mountains falling and seas rising and volcanoes spewing forth and various other geological conniptions associated with the flood.  For starters, absolutely none of it is actually in the Bible and it is an amazing case of eisegesis.  The problems continue:

If you look at the fossil record, you find things that should float at the bottom, which is where, coincidentally you don’t find any evidence of shipbuilding or habitation.

—next—


Rich - #47613

January 16th 2011

Martin (continued from 47606 above):

Martin, I think you will agree that you were taught from your earliest days as a Christian that the Bible was true and this was guaranteed *in advance of reading and understanding it*.  Doubts might arise as you read parts of the Bible, but you were taught that, in time, all those doubts would be resolved, because the Bible was true.  All apparent contradictions and errors will ultimately vanish.  We must trust in the guarantee.

I don’t hold this traditionalism against you.  But if proves what I have been saying all along about the absolute need for tradition.  You assume *in advance of proof* that your view of the Bible as seamless truth will be vindicated.  This assumption is not and cannot be guaranteed by the Bible, understood merely as a collection of ancient texts.  It is held because “the Church,” “Tradition,” “the Faith of Our Fathers”—call it what you will—vouches for the Bible as *more than* a collection of ancient texts.  The Protestant notion of sola scriptura *cannot be sustained* without this assumption.  Ironically, sola scriptura implies that *at least one tradition*—the tradition which delivered the Bible, *as* Bible—is reliable.


Jimpithecus - #47614

January 16th 2011

Instead, what you find is small things at the bottom that are perfectly sorted—in the case of trilobites according to the number of compound eye segments they have—followed by less primitive things, followed by fish of all shapes and size, then early tetrapods, then small dinosaurs followed by some very large dinosaurs three quarters of the way up the column, then the earliest mammals, then larger mammals, then the first primates, then the first proto-humans and then you get human dwellings and shipbuilding technology. Everything is perfectly sorted.  While it is true that you have some things missing from time to time it is never out of order. 

A turbulent world-wide flood would produce none of this.  The big things would sink to the bottom, the small things would float down and the human habitation remains would be at the bottom.  There would be no sorting whatever.  Further, in the standard geological column, there are no humans below the very top layers.  That is a bit hard to fathom (sorry) given that there must have been people that were caught in their sleep or had infirmities that prevented them from climbing to avoid the water.  Not one is found. 

—next—


Jimpithecus - #47617

January 16th 2011

There are other problems.  There are things that would never be found in a water environment of any kind: fossilized mud cracks, fossilized dinosaur nests and bird nests with hatched eggs, river paths, huge boulders all of the way through the column, and in-place forests, many of which show signs of forest fires.  There are footprints (Paluxy River, anyone?) of dinosaurs and mammals, sand dunes and huge salt diapers, such as that formed by Lake Bonneville that would have taken decades to form but simply could not form in a flood of any kind. 

There are fossilized coral reefs buried in places that have miles of fossilized remains and different geological strata beneath them.  Corral reefs are too heavy to float.

This only scratches the surface of the evidence that there never was a world-wide flood. 

Some of this is also common sense, though.  If you take a swimming pool and fill it with two parts mud and one part water and keep it out of the rain for one year, at the end of the year, you will have somewhat harder mud.  What you will not have is granite, shist, shale, obsidian, or any other kind of rock you can find in the earth, some of which show evidence of compression and heat. 

That help?


Martin Rizley - #47625

January 16th 2011

Rich,
Actually, I was raised in a theologically liberal (though morally conservative) United Methodist household.  During his life, my father never believed in the inerrancy of Scripture and my mother does not, to this day.  In high school and college, I came to a more conservative view of the Bible as I began to discover its contents for myself.  Evangelicals like John Stott in his IVP booklet The Authority of the Bible pointed to texts which showed Jesus’ view of the OT Scriptures and the authority He bestowed on the apostles as His official spokesmen.  I discovered those texts which describing the nature of biblical inspiration which clearly indicate its verbal inspiration and inerrancy.  It is not just conservative evangelicals, however, who believe that the Bible is inerrant.  Many Catholics hold the same view.  Even liberal theologians like Adolph Von Harnack admit that this was the viewpoint of Jesus and the apostles.  His own assessment was that “Jesus was a fundamentalist.”    So there seems to me to be no doubt—whether from the standpoint of faith or the standpoint of scholarship, what Jesus’ view of the Scriptures was (continued).


Martin Rizley - #47627

January 16th 2011

The question is, was Jesus correct in his view of the Scriptures?  And if so, is there reason to believe that God has given to the church inspired New Testament books in addition to the inspired Old Testament books that Jesus recognized as authoritative Scripture?  So here are some key questions to ponder, when it comes to having a proper view of the Bible:
1)  Did Jesus believe in a distinction between inspired and non-inspired books?
2)  Are we to understand, therefore, that God has inspired certain books and not others?
3)  Does God intend for inspired books to function practically in the church as a rule of life, governing both the doctrine and practice of the church?
4)  If so, does the church have an moral duty or obligation to receive those inspired books and submit to their authority as an act of obedience to God?
5)  Can God enable His people to distinguish inspired books from non-inspired books?  Can He give them discernment by His Spirit to receive the former as canonical and reject the latter? (continued)


Martin Rizley - #47628

January 16th 2011

It would be interesting to know, Rich, your answer to those five questions above.


nedbrek - #47629

January 16th 2011

Jim, thank you for taking the time to write such a detailed response.

When I see these things, I say “what tremendous energies are unleashed by God’s wrath against sin”.  I understand that people like Whitcomb and Morris cannot explain it.  I don’t think anyone can (at least not compared to resources available to naturalistic science to construct a story).

Is a naturalistic story so important to you?  Why?


Rich - #47633

January 16th 2011

Martin:

Thanks for the background on your religious life.  But however you started out, and whatever vicissitudes your thinking endured, it’s fair to say, the following, is it not?

1.  You *now* read the Bible under the assumption (non-negotiable) of a 66-book canon, and under the assumption of its complete inerrancy and mostly literal interpretation.

2.  When you hear of apparent contradictions, your attitude is not:  “Gee, maybe there are contradictions; let’s weigh the evidence on both sides and follow the argument wherever it leads, and if there are some contradictions, I’ll admit that the Bible isn’t in all respects a flawless communication from God, but merely a book which contains inspired truths alongside of human errors”; but rather: “I may not be able to see the answer at the moment, but I am certain that the contradictions are only apparent, because I know that every word of the Bible proceeds from the mouth of God and that God does not contradict himself.”

Is this not a pretty nearly accurate statement of your attitudes and assumptions?

And if so, do you not see why it would be impossible for scholars of religion to adopt those attitudes and assumptions in their academic work?


Rich - #47639

January 16th 2011

Martin:

All kinds of Christians do hold the Bible to be “inerrant,” but in the Catholic case and in most cases outside American fundamentalism, “inerrancy” is interpreted broadly and common-sensically, to mean that the Bible is inerrant in what it teaches *concerning matters of faith and morals*, and further, that what the Bible *teaches* is not necessarily identical in all cases to its narrative statements.  Thus, all Catholics believe that the Bible “teaches” the Fall, but they are not required to believe that the scene between Eve and the serpent is a news report, and they are allowed to believe that the Garden story contains a great deal of imagery that need not be taken historically.  This is a very wise way to proceed, for it allows those who need to hold onto the literal picture to do so, while allowing those of great education and literary sensitivity to receive the truth of the story in a way suited to their capacities.  The typical inerrantist on the Protestant side, however, uncompromisingly insists that everyone from the most educated literary scholar down to the most Philistine store clerk must understand the story in the same way, i.e., as a news report.


Rich - #47642

January 16th 2011

Martin (47627):

Your questions are easy to answer, but the answers don’t prove what you want them to prove.

1.  Yes, Jesus believed that some books were inspired.  He said nothing about non-inspired books one way or the other.  He also did not give a definitive list of inspired books.  He knew of no “Old Testament”.  He spoke of “the law and the prophets”, and he quotes or paraphrases from several of “the writings” which were not formally canonized in his time.  His words *cannot* be interpreted as determining the canon of the OT that was eventually settled on at the Council of Jamnia.  He made *no* comments about the canon or the principles by which it should be established.  Jesus’s religion respected holy books but was not a bookish religion, as Protestant inerrantism is. 

(continued)


Rich - #47645

January 16th 2011

Martin (answering your five questions):

2.  Knowing that God would inspire some writings is useless knowledge unless we have a rule for determining which writings.  And that rule is nowhere given *in* the writings, but is applied *to* the writings from outside, by the Church.  The Church makes an interpretive decision.  The Church can err, as you admit.  It may have erred in the canon.  For example, supposedly one criterion was apostolic authorship.  Well, why should only an apostle be capable of receiving the word of God?  Can’t God inspire anyone?  And even if the principle is legitimate, what if some texts deemed apostolic should later prove to be spurious?  Will the Church pull them out of the canon?  Apparently not; no competent scholar now believes that *all* the books of the NT were written by their traditional apostolic authors, but the canon of the NT is the same as it always was.  Why hasn’t the canon been reduced? 

Suppositions that God would guide the Church so that it could not err regarding canon are (a) gratuitous; (b) have no confirmation in the texts; and (c) useless until we determine which Church has the authority, since canons differ from Church to Church.


Rich - #47646

January 16th 2011

Martin (answering your five questions):

3.  I don’t presume to speak for what God intends.  If I knew what God intended, I would be a prophet rather than a scholar.  But it’s not unreasonable to think that God may have intended certain books to inspire and guide the church.  But it doesn’t follow (a) that God speaks to the Church *only* through the interpretation of those books, and never chooses to reveal anything directly to it, bypassing the books; (b) that God intends those books to be interpreted according to the principles of fundamentalist inerrantism.


Rich - #47650

January 17th 2011

Martin (answering your five questions):

4.  The Church has the duty to submit to all books which it knows to be revealed.  The problem is how to determine which ones are revealed.  Without criteria provided by God, the Church cannot carry out its duty.  Where has God set forth the criteria for inclusion in the canon, Martin?

5.  Can He inspire the Church to select the right canon?  Yes.  But more to the point, *did* He?  And again, since canons vary from Church to Church, *which* Church did He inspire to do the job correctly?  You are of the view that he inspired only the Protestant Church correctly, a rather condescending and partisan position in my opinion, and one which many scholars better trained than you in the history of the canon would vigorously dispute.  The up side is that I am sure that not very many members of the Ethiopic or Syrian or Greek Orthodox or Roman Catholic Churches are losing much sleep over what Protestants say about their canons. 

OK, Martin, I’ve answered your questions, now answer mine:  how can *sola scriptura* be maintained without at least *one* extra-scriptural decision—regarding canon—first being made?  And how can this decision be made unless the Church has authority?


Jimpithecus - #47652

January 17th 2011

Nedbrek wrote in #47629: “Is a naturalistic story so important to you?  Why?”

It is not that a naturalistic story is so important to me.  It is just that I believe that the world is a record of God’s creation and the biblical passages in early Genesis are sufficiently obscure. The problem is twofold: First, as I mentioned, there is zero evidence for a world-wide flood.  This was known as early as the 1830s, well before evolution.  The second is that the similarities between the Genesis flood epic and that of Gilgamesh and Atrahasis suggest a common origin for these stories that is buried in antiquity.  I am not completely willing to rule out Ryan and Pitman (Noah’s Flood) just yet.  One of the fascinating things about Genesis 1-11 is that it reads like myth and is absolutely unlike anything else in scripture.  It is a creation story for God’s people.  Does it have to be 100% literal to be true?  The six day creation in Genesis 1 wasn’t meant to describe exactly how the world was created.  It was designed to dispel the gods of the day, the night and the earth.


Jimpithecus - #47653

January 17th 2011

I am dropping out of the comments but will be happy to entertain questions about the post, itself.  I need to start work on the next one.  Thanks for the interest, folks.  Stay Tuna’d.


Martin Rizley - #47660

January 17th 2011

Rich,  Neither I, nor anyone else, simply ‘assumes’ there are sixty-six books in the canon, since no prophetic utterance of any inspired prophet or apostle ever said, “When the canon is complete, it will contain sixty-six books.”  No.  The particular number of books in the canon is a discovery that is made by means of an historical process.  By that I mean, in the fullness of time, the number of books imposed on the church by divine providence that possess the internal and external attributes of inspired Scripture just happened to be sixty-six.  But the divine mandate is not and never was—“You must receive the SIXTY-SIX BOOKS of Scripture.  The divine mandate is “You must receive AS MANY BOOKS as show themselves to be inspired Scripture by their internal and external attributes.”  The number of books that meet that criteria just happens to be sixty-six.  .  But the number “sixty-six”  is not known or ‘assumed’ beforehand.  It is a ‘discovery’ made by the church through an historical process in which godly leaders were used of God to lead the church into this recognition.  (continued)


Martin Rizley - #47661

January 17th 2011

To review the evidences, internal and external, by which these sixty-six books commended themselves to the church as inspired and canonical, would require more space than we have here.  There are good books written on the subject that tell us how we came to possess the Bible that we have.  These books also explain the reason why Protestants did not receive the Old Testament Apocrypha as inspired, but rejected those books as canonical, as did notable figures in the early church like Jerome.    I think it is perfectly legitimate for Christian scholars to pursue scholarly research on distinctively Chirstian presuppositions.  That would include presupposing that God has given to the church inspired Scripture—since Jesus the Son of God obviously believed that such a thing existed—and that the Scriptures ‘cannot be broken’—that is, prove false or untrue in their teaching.  That cannot be, since what is inspired is ‘breathed out’ by the Spirit of God and represents God’s infallible revelation of His mind and will to men.  Anglican J. I. Packer defends the legitimacy of scholarship pursued on these assumptions in his book, Fundamentalism and the Word of God.


Page 9 of 12   « 6 7 8 9 10 11 12 »