Science and Human Evolution

Question from EvoE:
What is the proof humans have evolved from a common ancestor? If the scientific method is observation, data collection, internal and external validity and reliability; then how can one observe human evolution?

Answer by SmartLX:
We don’t observe human evolution. Scientists genuinely don’t know whether it’s still happening, and discuss it often.

This means little, because science does not always require direct observation of a past event to confirm that it’s happened. If it did, the police would have to be present at every murder in order to charge any suspects. We can instead observe and collect evidence that humans have evolved from ancestors we share with other animals.

The evidence includes but is not limited to:

1. Comparative physiology
We often say we evolved from apes, but it’s just as correct to say that we are apes. Without even considering genetics, we can be classified as apes using physical characteristics such as our long arms, omnivorous teeth and lack of a large tail. It goes far beyond superficial physical qualities, because our internal organs and body chemistry have countless analogues in other primate bodies. We’ve even got some organs that are practically useless to us but essential to other primates, such as the appendix and the muscles for moving our ears. (These and other human vestigial organs speak loudly against the Intelligent Design proponents’ claim that all the similarities are due to the other animals having the same Designer. Why wouldn’t He just leave out the useless organs, rather than leave them in place to potentially kill us?)

2. Genetics
The genes linked to the analogous systems mentioned above can be sampled from each species and compared directly. Now that the whole human genome has been sequenced, it can be compared all at once to the genomes of other animals. The results are as expected: our DNA diverges less than 2% from some species of apes, such as chimpanzees and gorillas. (By comparison, the most distantly related humans differ from each other by about 0.1%.) As we compare ourselves to other non-primate mammals, reptiles, plants and so forth, the genetic difference rises accordingly, exactly as we would expect if we diverged from these other branches of life earlier on.

Even knowing single comparative facts, like that chimpanzees have one more chromosome than we do, we can predict and discover evidence of very specific biochemical events that happened during our own evolution, such as the mark where two of our ancestors’ chromosome pairs fused to make one of our own pairs, specifically Chromosome 2.

3. Observed natural and artificial selection (and speciation)
We have watched some species with relatively short life cycles breed and diversify to the point where two populations of the same animal became unable to breed with each other. We’ve conducted breeding programs which have deliberately achieved the same thing, just to see what’s needed for it to happen. These are instances of speciation, or the splitting of one species into two, because part of what defines species is that they can’t produce fertile offspring with other species. There have been billions of years for this kind of thing to happen all over the world without any external help, and there’s no reason to think our own origins are any different.

If you want the rest of the evidence, start at the Wikipedia page for evidence of common descent. It’s not solely concerned with humans, but a lot of it has to do with us. If there’s something specific there that you don’t accept, bring it up in a comment.

Are you sure you’re in the right classroom?

Question from Pete:
Hey, um, what’s the length of an Oleic Acid Molecule?

Answer by SmartLX:
1.97 nanometres by 0.5 nanometres. The accepted dimensions are provided here, along with a popular chemistry experiment that allows you to estimate them for yourself.

It’s possible that you’re going to follow up with an argument for God based on the apparent uncertainty of the things we “know” from science, so go ahead if you’re going to. Otherwise, I hope I helped with your homework.

Ask from the Past: What makes science and history more true than religion?

“Once you stop looking for absolute certainty, you start to judge these things on their actual merit.”

(When the archived ATA site was restored, a short list of unanswered questions was found in the approval queue. I’m answering them here in Ask from the Past, and this is the last one.)

Question from Nym:
Hello.

I was recently in a debate against something on the topic of religion (namely, Christianity) vs science. I was debating for the scientific side. It was going well, but then he brought up a couple of questions that I didn’t know how to respond to.

1. What makes science so accurate?

Here, he was explaining to me how science is “proven wrong a lot more than Christianity is.” He brings up the example where he claims that the Bible says the world is spherical (he says the word used in Hebrew means “spherical”), whereas science didn’t prove this until much later. He later goes on to say that since science is proven wrong so many times, how can we accept it as truth? I explain that we can’t completely prove anything, but then he says why we should accept science over religion if it is sometimes wrong. His final statement regarding this part of the debate is “[One] should spend less time arguing why religion is wrong and more time arguing why science is accurate.” The one thing I did not want to fall back on is the word “faith.” I mean we can reproduce experiments and get similar results, but how do we know that this is really the true nature behind what we are observing? The scientific method does exist so that it can adjust when something is proven wrong, but we can’t really be certain when we’ve reached the pinnacle of truth.

2. Is believing in history not the same as believing in religion?

I brought up how Jesus’ existence is disputable, using the 40 year gap between his supposed death and the story of Saul of Tarsus; how there was no historical account of Jesus in that gap of time. He rebuttals, “They were all persecuted.” I couldn’t respond to this one. Any more explanations I could use would be very helpful.

Something else he said included “How can you believe anything in history over the Bible?” I see where he was getting at. For example, how can we prove that Napoleon existed? History says that he did, but what can do to prove that? We may have historical accounts of people who were supposedly there during that period, but how do know if those are reliable; at least, any more reliable than accounts in the Bible? We can’t really prove anything other than what we observe, and even then, who’s to say that our eyes don’t deceive us?

Thank you very much for reading.

Answer:
A lot of apologists think of using the “historical” Jesus and Biblical ties to modern science as bringing out the big guns. They’re tough to rebut if you don’t have the answers on you, especially if you’re not familiar with the Bible quotes they use.

I’ll tackle the spherical earth claim first: the passage is most likely Isaiah 40:22 which says, “He sits upon the circle of the earth…” The Hebrew word in the original text that translates to “circle” is gh, which unsurprisingly means “circle”. It’s rwd that means “sphere”. (I got that from a bible study site, mind you.) If this is what your opponent was referring to, he was wrong. The author of the Book of Isaiah (whether Isaiah or not) might have been referring to a flat earth, or the circle of the horizon as visible from a high place, or any number of things.

It’s true, scientific information is found to be false all the time. That information which replaces it is nearly always more accurate. Furthermore, it’s usually found to be false in small ways; that the Earth is 100 million years older or younger than was estimated last time, for example. That’s hardly a reason to chuck it all out and say it’s 6000 years old instead of over four billion.

While I’m on the age of the Earth, it’s been found to be billions of years old in many different ways. Whenever anything on the planet is dated to more than ten thousand years ago, a doctrine of Christianity (among others) is proven wrong again. Every generation that goes by without Jesus returning is a further contradiction of his supposed prediction that he’d be back within just one, unless he meant something out of the ordinary by “generation”. Christianity at least rivals science when it comes to being wrong.

Absolute truth is probably unattainable as long as the absolutes of the universe (if any) are unknown to us, but we can try to get closer all the time. Long before we reach that point, we reach a point where even if our underlying hypotheses are wrong, they approximate the truth closely enough to be useful. When science reaches that point, it’s able to make concrete predictions which can then be tested. This is one major area where it deviates from the Bible: what predictions can that be used to make which can be tested in the near future, as opposed to interpreting it in hindsight to match events which have already happened (much, much easier, and not just with the Bible)?

Getting on to Jesus, the authors of the New Testament were likely persecuted even after they’d written and distributed it. What I find more interesting is that they would have been very old when they did, as 25-30 years was the life expectancy at the time, or if later people wrote it then it was all second-hand.

While we can never be absolutely certain of history, a bit like science, evidence accumulates which can give us a great deal of confidence in it. Here’s a sample of what we have of Napoleon that we lack for Jesus:
– Consistent likenesses, from life-size statues to portraits for which he posed in person to coins which were minted and used during his lifetime.
– Writings by the man himself, starting from a manuscript he wrote at 17 and ending very shortly before his death in exile.
– First-hand accounts by hundreds of people, all of them undisputed real people, of personal dealings with him and his appearances before hundreds of thousands of soldiers and citizens, written within days of the events…rather than accounts mostly written in the third person by a handful of authors so disputed as to be effectively anonymous, of his appearances before hundreds, most of whom were illiterate (the literacy rate in first century Israel/Palestine was about 3%), written years or decades later.

Once you stop looking for absolute certainty, you start to judge these things on their actual merit. One can be far, far more confident in a historical Napoleon than a historical Jesus. It worries me that this was not plain to your opponent.

SmartLX