"My grandfather wasn't no monkey!", "You think we came from slime?!", and "man, if you want to believe your great^100 grandpa was a rock, be my guest...but it's STUPID!". The latter was actually left on a use.net forum awhile back. They're all too familiar to those of us who defend evolutionary biology from the constant onslaught of religious opportunists who prey on their theistic victims for personal or political gain.
Talk Origins contributor Aron-Ra and I take a stab at responding to these objections based on Aron's Post of the Month, July 2002. Want a short break from politics and Rovism? Read on!
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Great to the 100th? Well, yes, that would be pretty stupid. A monkey? Slime? Rocks as ancestors? Clearly you don't have an adequate grasp of either the actual concept of evolutionary ancestry or of the significant time factors involved. I think you need a whole lot more zeros as well as a more realistic ultimate original entity. And maybe it would be worthwhile to learn more about Creation before taking up the call to tell your Creator what He can and cannot do.
I figure at 20 years per generation, 100 generations of grandfathers would equate to twenty centuries. That means the grandpa you're talking about was a contemporary of rabba Yeshua bar Yosseff just 2,000 years ago. Not quite an adequate evolutionary time-scale and certainly far from the mark when talking about the origin of life on Earth. But even 100 years ago, 16 years per generation was more the norm as it was with my grandparents and many of their ancestors. That would have put your great^100 grandpa in the time of another wildly exaggerated hero, King Arthur, in about the 5th century of the common era.
Increasing the multiple, your great^1,000 grandpa would have had even shorter generation gaps, being about 14 or 15 years apart on average. He would have been a Paleolithic nomad in about 13,000 BCE, just shortly before the foundation of the most ancient cities like Jericho and Damascus. He still would have been fully human and already a member of the only surviving human species, Homo sapiens. Like this:
Your great^10,000 grandpa and grandma would have been everyone else's great to the Nth grandparents too. (Everyone alive today that is) He would still have been definitely human and visibly different from his Neanderthal neighbors. Whether he would be considered Homo sapiens yet 140,000 years ago or still classified as H. antessesor or heidelbergensis doesn't really matter. All are still obviously people and no more ape-like than any of the more isolated aboriginal primitives still around today.
Your great^100,000 grandpa might now be called Homo ergaster or erectus having lived some 1.3 million years ago, reconstructed by a forensic artist below.
And his great^10,000 grandfather would have been called Homo habilis or rudolfensis. Any or all of them would have appeared to be a bit more ape-like than the most monkey-faced modern guy, but he still would have been definitely human, especially when compared to the other fully bi-pedal apes that were wandering around a million and-a-half to a couple million years ago. If you were to put your erectine or habiline grandpa on a crowded pew in your church, he would have looked like an ape-man. But if you saw him amongst his natural neighbors, the paranthropines, you would have seen him as nothing less than a man. However, the generations would be shorter, now being something like 13 or 12 years apart on average.
Homo Habilis circa 2.5 Million Years Ago
Your great^1 million grandpa on the other hand is quite a leap away from Homo erectus. A lot can happen in 900,000 generations and the world was much different 10 million years ago. There were no definite humans yet, but there were other hominids even though none of them could walk on two legs for very long. There were creatures similar to modern gorillas, chimpanzees and orangutans, but they were different than the ones we have today. One of the orangs for example stood as much as 8 feet tall. And the space between generations would have been only eight to ten years and much less as time goes on in reverse.
Generic Miocene Ape, circa 10 Million Years Ago (MYA)
At six or seven years between generations, your great^10 million grandpa would have been barely recognizable as a primate, looking almost as much like a squirrel. And he might have witnessed the demise of the dinosaurs, or he would have grown up in the harsh wasteland that was the wake of the KT impact for so many years. Now the generation gap really begins to close. For most of the Mesozoic era and a long time before that, the age difference between father and son would only be about a year.
Plesiadapis circa 60 MYA on the left next to a Purgatorius dated to 70 MYA
Your great^100 million grandpa was a shrew-like mammal darting through the Jurassic underbrush 170 million years ago. The amniotic sacs his children were born in didn't have quite the same integrity that his grandfather's birth-sacs had. Although leathery and easily torn, they would still have been considered egg "shells" much like some snakes are born in today. This grandpa would have been mammalian, but not yet placental.
Cynodont 170 MYA
Your great^1 billion grandpa would have lived under water along with everything else, including trilobites and some really alien beasties a few hundred million years ago and at least a couple hundred million years before the first dinosaur. The generation gap is now a monthly rather than yearly division. But for most of the last half-billion years of our genealogy, that wasn't the case. In 400 million years, your ancestors went from toothy swimming worms like conodonts and pikia and became crossopterygiian fish and then tetrapoidal amphibians, synapsid reptiles and even amniotic proto-mammalian cynodonts. But the generations before that were infinitely less interesting.
The Fish-amphibian transitional, Acanthostega 360 MYA
Above: Conodont, primitive fish 430 MYA
Worm-like Pikaia: The first know chordate dated at over 500 MYA
The world of your great^10 billion grandfather wasn't much different from that which was already described, although there were a lot fewer trilobites then. And he wasn't a swimming worm yet. He would have been a roundworm, if he would have been considered a worm at all. He may have looked more like a jellyfish with a sense of direction. Before that, he may have been something even simpler, like a microbial sponge, but still definitely a metazoic animal even if he wasn't really a "he" in the sense of discernible gender anymore.
Siphonophore such as those which may have existed 700 to 800 MYA and a tiny hydra standing in for even earlier multicelled colonial organisms
Your great^100 billion grandfather may not have been an animal yet, but a sort of co-op of bacteria living inside a single membrane: The mitochondrion, Golgi apparatus, nucleus, and other bacterial endosymbionts, all of which have their own individual ancestry.
Eukarytoic Cells first appear in the record 1.7 billion years ago
Your great^1 trillion grandfather would have been various bacteria before they learned to cooperate in a single eukaryotic cell.
And your great^10 trillion grandfather would have been bacterial too.
Three-billion years ago
Your great^100 trillion grandfather may have been an even simpler chemosynthetic protien in an inhospitable world unrecognizable as Earth.
Even earlier, with 'generations' now coming every few minutes and represented by chemical hypercycles, your 'ancestors' would have been macromolecular cycles in which the end result of a given chemical reaction is the constituents to fuel the next leg which ultimately circles back around to any one reaction. This is the earliest we can go back in terms of proto-biology, even in speculation. We are now at just over 4 Billion years in the past.
Schematic of a hypercycle
Those substances in turn came from the smaller planetoids and dust grains which formed the earth itself starting five billion years ago.
Although the concept of 'ancestors' and 'generations' no longer has meaning, your ancestral molecules can be found in volatile ices and hydrocarbon tars making up cometary bodies in the Solar Nebula before the earth congealed. And much of the material in your body, the minerals for example would have been present in the solar nebula as "just rocks".
The material which condensed into a disk to form our solar system including the earth was a combination of interstellar hydrogen and heavier elements such as nitrogen or oxygen. These heavier elements, each and every atom, were cooked up inside a large star and released in a super nova. You are made of stardust like this:
Super Nova Remnant M-1: The Crab Nebula
The primordial elements Hydrogen and Helium which made up the first massive stars themselves? That was produced in the Big Bang in a process called Big Bang Nucleosynthesis.
Humans have a tendency to form opinions about what is possible and what is not based on intuition derived from everyday experience, and on emotional acumen. But is this always useful?
Everyday experience will not help you when it comes to continental drift, traveling close to the speed of light, or ice sheets marching and retreating across the landscape. We ephemeral creatures place such events not in the class of rare, or time consuming, or unusual, but of never. And that's just one example of how our common sense can fail us when dealing with the most uncommon of phenomena.
The emotional objections likely revolve around two concerns: 1) The idea of being 'just an animal' or 'coming from slime and rocks' and 2) worry that science undercuts religious faith.
It's true science can undercut some tenets of faith. If the idea of a flat-earth or the Sun-god is a part of that faith then you either ignore the science and live in ignorance, or you adjust your theology. Those really are your only two choices.
What your objection more than likely reveals is that you don't like the idea of being the product of 'random' physics and biochemistry, that you feel there is no room for a Creator in such a scenario. I cannot imagine greater natural evidence for the Brilliance of a Creator than myriad complex processes unfolding over billions of years through countless steps in exquisite order spanning the entire Cosmos. The technical skill and artistic vision of such is to be admired in awe, and in that context evolution should be worthy of your devotion, not your disdain.
Just a monkey? Just slime? Just a rock? ... You speak of these things with latent fear disguised as contempt. But a Creator is not limited to our prejudicial desires about how Creation must unfold. If I were religious, I would teach my fellows to feel honored at being descended from a long line of God's wondrous creations and for sharing the amazingly complex biochemical processes those ancestral benefactors endowed us with. If I were a Sunday School Teacher I'd tell my young students that through the wisdom and creative genius of the Lord we can include Cheetahs and Peregrine Falcons in our extended family; I think they'd eat that up!
And I'd praise our evolutionary lineage and thank our Linnean cousins from the primates to the microbes and, yes, all they way back to the comets and the 'rocks'. For through them God bequethed unto us the finest instrument and possession you and I will ever own: Our bodies and our intellect.