Wednesday, June 15, 2016

What is Homo naledi, anyway?

There's a new study on the phylogeny of Homo naledi published today in the August issue of Journal of Human Evolution (it's a preprint).  The study is written by Mana Dembo and colleagues.  They compiled a massive matrix of 391 characters (a supermatrix), all from the skull and teeth.  They scored these characters on 22 different hominins and chimps and gorillas.  For H. naledi, they compiled only 123 of those characters from the original bones at Wits (Dembo was on the H. naledi research team).  That's considerably more than the 87 published in the supplemental material of Berger's original description of H. naledi, which I used previously to do my own phylogenetic analysis.

For this analysis, Dembo et al. used Bayesian methods to infer the phylogeny.  I've always been a bit suspicious of Bayesian methods, mostly because of the need for a model for which the probability is known.  That's technically not knowable, but Bayesian methods get around this by drawing model probabilities from a set of "random" models.  So it ends up sort of like a bootstrap in traditional parsimony studies.  What Bayesian methods get you is the ability to test many more models and model parameters than you could with other phylogenetic methods, and that's really a big deal.  In this new paper, Dembo et al. include a fairly nice summary of Bayesian methods for those already familiar with other phylogenetic methods.

They did two sorts of studies.  In the first, they just looked for the best phylogenetic model, which I've copied below (on the left, from their Figure 2).  In this tree, H. naledi ends up basal to a clade that includes modern humans, Neandertals, H. heidelbergensis, and the poorly known H. antecessor (which is thought by some to be ancestral to H. heidelbergensis and by others to BE H. heidelbergensis).  In their second analysis, they specifically tested alternative trees that tested the specific relationships of H. naledi.  They found that H. naledi is definitely a member of Homo, but  they couldn't rule out several alternative trees to the one shown, indicating that the precise phylogenetic position of H. naledi within Homo could not be conclusively determined.

What's interesting is that you can see that in their original analysis as well.  They include the posterior probability values for the clades in their published tree.  Given the way they did their modeling, these probability values end up being like a kind of bootstrap value, so I created a version of their tree that only shows majority-rule clades and leaves the rest of the branches as unresolved polytomies (below, middle tree).  This shows a lot of ambiguity within the Homo + Au. sediba clade, which is very consistent with my own published phylogeny of H. naledi based on 87 characters (Wood 2016, below right).  In both trees, the relationships within Homo are unresolved.


As I explained above, Bayesian phylogenetics allows you to test specific models in ways that traditional phylogenies do not.  Unlike these traditional majority-rule consensus trees, Dembo et al.'s analysis found that Homo relationships were not completely unresolved.  They found that H. naledi is definitely not the sister taxon of African H. erectus, Georgian H. erectus, H. rudolfensis, H. heidelbergensis, and Neandertals.  So the unresolved Homo clade is not really that unresolved:  We can say with some certainty what Homo naledi is not closely related to.

Dembo et al. also report a possible date for Homo naledi of around 900,000 years ago, based on fossil dates and their model of character changes.  I'm not that excited about this date, since the 95% high posterior density interval ran from 2.4 million years ago to the present.  So basically, there's a pretty good chance Homo naledi lived some time in the past 2.4 million years, according to conventional dating, which we already knew.

What does this mean for creationists?  Probably not a whole lot just yet.  It would be nice to affirm that H. naledi is closer to modern humans than H. erectus, since most creationists think that H. erectus is human.  That would boost my own assessment that H. naledi are definitely human descendants of Noah and family.  But Dembo et al.'s results cannot support that kind of specificity.  We just can't say for sure yet.

So what is Homo naledi?  To date, the most comprehensive creationist analysis says they're human.  The new Dembo et al. study shows that they're definitely Homo but probably not Homo erectus.  Other than that, none of us are very certain.

Dembo et al. 2016. The evolutionary relationships and age of Homo naledi: An assessment using dated Bayesian phylogenetic methods.  Journal of Human Evolution 97:17-26.

Feedback? Email me at toddcharleswood [at] gmail [dot] com. If you enjoyed this article, please consider a contribution to Core Academy of Science. Thank you.

Thursday, June 2, 2016

Support student internships

Core Academy supports student internships and needs your help!  There's a challenge gift of $650 to support this work, but we need your support to claim it.  Read all about it here, and remember that contributions to Core Academy are tax deductible.  And don't forget about Pies & Prayers!

Help us meet our Midsummer Challenge Gift


Feedback? Email me at toddcharleswood [at] gmail [dot] com. If you enjoyed this article, please consider a contribution to Core Academy of Science. Thank you.

Friday, May 27, 2016

About those Neandertal stone rings

I've got a new post on Human Genesis discussing those stone rings in the Bruniquel Cave.

Neandertals Continue to Surprise in the South of France


Feedback? Email me at toddcharleswood [at] gmail [dot] com. If you enjoyed this article, please consider a contribution to Core Academy of Science. Thank you.

Wednesday, May 25, 2016

Lord, make me a better enemy


A while back, I posted an article about the anthropology meeting that I attended in Atlanta, where I wrote this:
I suppose some might think that I should be more indignant because of all these evolutionists undermining the truth or some such, but I'm far more unsettled by fellow evangelical Christians promoting evolution than by non-Christians doing it.  They really should know better.
Almost immediately, I got an email from a guy challenging me to explain what I meant and recommending that I check out the BioLogos website where I could learn more about Christian approaches to evolution.  This week, Jim Kidder posted a response on his blog, and he also took me to task for the very same phrase.  Jim wrote, "My initial reaction to this statement was to think that I had been insulted."  I must have hit a nerve.

I suppose I should apologize or defend myself, but as usual, I see bigger things here.  I didn't set out to insult anyone, but people took umbrage anyway.  The reactions led me to wonder why anyone who's been involved in this creation/evolution debate would ever expect anything different?

Let's just lay all the cards on the table.  Everyone in the creation/evolution debate insults everyone else all the time.  I can't see how it's possible not to.  Young-age creationism is an intellectual embarrassment, a scandal of the evangelical mind.  It's bad science and bad theology.  The strident commitment to this pseudoscience brings shame on the gospel and drives people away from Jesus.  Sound familiar?  Well, that's pretty insulting when you're on the receiving end.

Evolutionary creationism is a lie.  It's an ungodly compromise with the world.  It's promoted for the approval of people not the approval of God.  It's basing our thinking on man's fallible opinions rather than God's unchanging Word.  Evolutionary creationism undermines the authority of God's word, and it's an attack on the very person of Jesus Christ.  Any of that sound familiar?  Well, it's pretty insulting, too.

Here's the problem: We don't say these things just because we want to hurt people.  These are deeply held convictions, and we believe them.  Most of us have come to our beliefs through soul searching and (sometimes agonizing) effort.  Everyone has sacrificed something for these beliefs.  Some of us have sacrificed a lot.  Maybe we find more tactful ways to say these things, but most of us can still read between the lines.  No matter how we express these convictions, we're bound to insult someone.

But it's worse than just personal insults.  We have entire organizations dedicated to spreading their views and undermining everyone else.  They all have basically the same sort of message: "My ways of reading the Bible and science are the only correct ways, and everyone who disagrees is absolutely wrong and dangerous."  One organization might be "nicer" than another, but that doesn't change the underlying message.  These organizations are all trying to get the evangelical public to accept their view as correct and to ignore that other guy (who is totally wrong and destroying the church).

Think about it.  Imagine that a group of Christians thinks you're so dangerous that they band together to oppose you and thwart your work.  How could you not be offended?  Maybe they try to be nice about it, and they don't really mean anything personal, but that doesn't make it any better, does it?

Sometimes I sort of wish it was just a matter of perspective.  It might be nice to say, "Hey, Jesus is our saviour, so let's just not fight over these secondary issues."  We don't do that though, because none of us believes that these are secondary issues.  For most of us, these issues hit on our very ability to know anything.  For me, I can't see how we separate a straightforward reading of Genesis 1-11 from all its doctrinal richness that touches directly on the nature of sin, the purpose of salvation, and the coming judgment.  If I can't believe what seems so obvious in Genesis, why should I believe what seems so obvious in Matthew?  Likewise, an evolutionary creationist looks at nature and thinks that evolution is so obvious that to question it is to question our ability to understand anything.  It's so obvious that if it weren't true, God would be guilty of falsifying evidence.  If evolution is wrong, either God is a liar, or all of science collapses.  These are not secondary issues.

As disturbing as it is to admit, the body of Christ is at war.  That's just incomprehensible, but there it is.  Other Christians have become my enemies.  I've written about this before, and I still won't sugar coat it.  We're battling over fundamental, irreconcilable differences.  We can't all be right.  We can't all win.  We won't agree to disagree.  It's just too important to let it go like that.

That war, more than anything I've written here, breaks my heart.  How did we get here?  How did the church go from the thrill of Christ's resurrection to shrill accusations of heresy?  How could the world ever know we are Christians by our love for one another?  Does it really boil down to "I'm right, and everyone else is wrong?"  How is that not sinful pride?  What can we do about this?

I've thought about this a lot.  I've written about my ongoing conversations with Darrel Falk, who is an evolutionary creationist and strongly disagrees with my position on young-age creationism.  Last year, we had a little exchange on my blog (parts I, II, III, IV, and V) and that seemed to hit a nerve with a lot of people.

After all my experiences with Darrel, I can say that I still have no idea what to do about this war.  We get together for a weekend, and we pray together.  We read scripture together, and we talk about our differences.  Then we go our separate ways, and I always feel a gnawing, nagging ache.  Even though our personal relationship grows, the intellectual divide is still there.  I wish that were not the case.  I wish that we would see the light, whatever that light is.  I pray that the Spirit would guide us into truth, whatever that truth is.  But the differences seem as strong as they were when we started.  To be honest, I sometimes despair that we'll ever be able to work out even the smallest of differences.  And if we can't do that, with all our intense effort, then what hope is there for the rest of the war?

More than anything else in this war, in those moments of despair I find what it is to trust Christ.  As I work so hard to explain why my beliefs are important and compelling, I know Darrel will not be convinced.  Darrel won't convince me either, and he knows it, too.  The situation seems hopeless, and that's just the kind of situation that Jesus loves to put us in.  After all, if this were just a misunderstanding, we could work it out ourselves, but this isn't just a problem we can figure out on our own.  There will be no progress here without intense prayer.  Only Christ can break this deadlock.

So the war drives me to Christ, and I pray the strangest prayer I could imagine:

Lord, make me a better enemy.

I don't know what that means exactly, but if I have to be in this ideological battle, then I need to be a better person for it.  Heaven knows I haven't done a very good job in the past.  I need to figure out how to love my enemy, even if I don't want to.  I can't change anyone else, but I can let Christ change me.  So I need to find Christ in the struggle.  In those moments of hopelessness, I have nowhere else to turn.

To those offended by my "really should know better" crack, I'm sorry I offended you.  I'm sorry we're even in this war.  But I'm not sorry for my convictions.  I believe what I believe.  I believe God wants me to believe what I believe, and I don't think I can say much about my beliefs that won't offend you.

Maybe we should pray about it?

Feedback? Email me at toddcharleswood [at] gmail [dot] com. If you enjoyed this article, please consider a contribution to Core Academy of Science. Thank you.

Monday, May 23, 2016

Registration for Origins 2016 is now available

The annual conference of the Creation Biology and Creation Geology Societies will meet at Liberty University in Lynchburg, VA on July 20-23, 2016.  That's just two months from now!  For more information on registration and tickets, visit the registration website:

http://origins2016.eventbrite.com


Feedback? Email me at toddcharleswood [at] gmail [dot] com. If you enjoyed this article, please consider a contribution to Core Academy of Science. Thank you.