55. Does the human yolk sac infer evolution?

embryo-6 weeks old-1

One human yolk sac, hold the yolk (six weeks gestation).

The human yolk sac emerges during the first few days of gestation and provides some of the first cells and circulation necessary for life. After about seven weeks, the yolk sac’s role diminishes as it is supplanted by the placenta.

But in oviparous (egg-laying) animals the yolk sac goes on to be filled with yolk, which allows the fetus to continue feeding while outside the womb.

Because most mammals get their nourishment directly from the placenta and lactation, yolk is unnecessary. 

But does the existence of a yolk sac in humans infer evolution?

Evolutionists say yes, insisting the yolk sack is a vestigial remnant of our egg-laying past.

Creationists say no, and point out that the yolk sac plays an essential role in the development of the embryo.

Evolutionists agree that the yolk sac is vital, but argue that it no longer plays the role it once did.

Creationists assert it never played that role, and that God must’ve designed the yolk sac to play two distinct roles.

And historically this is where the debate would end, in a draw, because you can’t prove that human yolk sacs once carried yolk… or can you?

What’s that you’re hiding in your genes?

Recently, researchers decided to see if human DNA contained the genes responsible for creating yolk. I’ll let Professor Dennis Venema explain the particulars:

One protein used as a yolk component in egg-laying vertebrates is the product of the vitellogenin gene. Since placental mammals are proposed to be descended from egg-laying ancestors, Chicken embryo at 16 days. researchers recently investigated whether humans retained the remnants of the vitellogenin gene sequence in pseudo-gene form. To assist in their search, this group determined the location of the functional vitellogenin gene in the chicken genome, noted the identity of the genes flanking the vitellogenin sequence, and located these genes in the human genome. They found that these genes were present side-by-side and functional in the human genome; then they performed an examination of the human sequence between them. As expected, the heavily mutated, pseudogenized sequence of the vitellogenin gene was present in the human genome at this precise location. The human genome thus contains the mutated remains of a gene devoted to egg yolk formation in egg-laying vertebrates at the precise location predicted by shared synteny derived from common ancestry.

While the vitellogenin pseudogene is compelling, it is but one example of thousands that could be given.

If creationists are correct in saying that the human yolk sac was never designed to carry yolk, what are we doing with a “scrambled” yolk gene?

The Creationist Response

In light of this new evidence, creationists kick the can further down the road by speculating that the vitellogenin gene is still active, and serves some other purpose in mammals.

It is presumptuous to assume that just because these genes were first found in association with egg yolk that their mammalian counterparts are vestigial remnants or that they, like so much other so-called junk DNA, will not be found to actually have functions unrelated to any ancestral history of making yellow goo.
Dr. Elizabeth Mitchell for Answers in Genesis

Dr. Mitchell goes on to point out that the vitellogenin gene is known to serve other purposes in honeybees and some non-mammalian vertebrates.

And maybe she’s right, just because the vitellogenin gene is associated with yolk production in non-mammals, doesn’t mean the gene is associated with yolk production in mammals… well.. except for that it is.

Echidna-Photo-550x461Luckily for us there are a few mammals that actually do have a functional vitellogenin gene; namely the monotremes: the platypus and two species of echidna. And guess what these mammals can do that no other mammal can do? You guessed it, they can produce yolk.

So it doesn’t seem presumptuous to assume that this is what the gene does (or once did) in mammals.

So why has this gene mutated?

It’s worth noting that when a copying error occurs in a vital gene, the carrier becomes less likely to survive or reproduce. But if a copying error occurs in a non-vital gene, the damage is inconsequential, and therefore the error is allowed to remain.

For example, if a chicken were born with a damaged gene that caused its eggs to contain no yolk, this mutation would be an evolutionary dead-end. Nature wouldn’t allow it. But if the same damage occurred in a placental mammal, it would be inconsequential, because the animal could get equivalent sustenance elsewhere. 

Natural selection selects for advantages and selects against disadvantages, propelling life forward through a simple process of trial and error. But inconsequential changes are just that. 


We have these three clues: an empty yolk sac that’s just like a bird’s, a gene that’s necessary for generating yolk, and evidence that this gene can produce yolk in mammals. Sure, we can always say, “God just wanted to design it this way,” but even if true, God designed it in such a way that also strongly infers evolution.

Professor Dennis Venema writes elsewhere:

These data make perfect sense if humans are descended from egg-laying ancestors and share common ancestry with chickens. It is very difficult to rationalize this data from an antievolutionary perspective. Since the common ancestor of humans and chickens was a reptile, this indicates that the vitellogenin pseudogene should be present in all non-egg-laying mammals. Studies so far have found this unitary pseudogene in wide variety of additional species ranging from dogs to wallabies.
Dennis R. Venema, An Evangelical Geneticist’s Critique of Reasons to Believe’s Testable Creation Model: RTB and Human-Ape Common Ancestry

From an evolutionary perspective, our yolk gene has suffered the same fate as our vitamin C gene: both were once vital, but became nonessential after we had alternative sources for obtaining similar sustenance.

Interestingly, creationists argue that our vitamin C gene was once functional in the Garden of Eden, but broke sometime after the fall of man. But creationists can’t very well argue that our yolk gene also once performed perfectly in the garden, so they argue that the gene must do something other than the obvious. 

We can always make up new excuses, but if looks like a duck, and quacks like a duck, it probably is a duck. Or in our case, if we have a yolk sac like a duck, and the genes for producing yolk like a duck, then maybe we’re related to the duck.

Other Sources:
Science Daily, Loss Of Egg Yolk Genes In Mammals And The Origin Of Lactation And Placentation, Mar. 2008
Forbes.com, The Fossils in Our Genes, John Farrell, Oct. 2011
The Mammalian Yolk Sac Placenta, Department of Zoology, The University of Melbourne, Melbourne, Victoria, Australia, Sept. 2009.
Creation.com, The human umbilical vesicle (‘yolk sac’) and pronephros—Are they vestigial?, May 2009
ChristianAnswers.net, Does the human fetus temporarily develop gills, a tail, and a yolk sac?
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28 Responses to 55. Does the human yolk sac infer evolution?

  1. Are comments working again?

  2. Jim says:

    Very cool stuff. I have never heard either of these arguments, yet have always wondered why there is a yolk. Just leave it up to Answers in Genesis, they will always create an answer. 🙂

    • Anonymous says:

      It is what evolutionists do, and really must do. Your remark is not very informed. The nature of science requires scientists to look for hypotheses that will further their claims or falsify them. They don’t give up because of a few anomalies.

      John Smithson

  3. Alpha says:

    Wow good one. I’ve never heard of this one before. Maybe I’m getting behind the times. 😛

  4. When I was taught Creationist Science growing up, I was told about all of the evolution hoaxes created by immoral atheists to prove God doesn’t exist, like Piltdown Man and how stupid, immoral atheists believe the human embryo shows the history of man’s evolution through visual similarities. No mention of a yolk sac was ever made.

    We ate a lot of hand picked cherries though.

    • Unfortunately scientists who were greedy for notoriety gave creationists more fuel for the fire. But these scientists were all eventually proven false… usually by other scientists. But throwing out the theory because of a few bad apples is like tossing out Christianity because a few priests are child molesters and a few televangelists are thieves. There are misguided individuals on all sides.

    • Anonymous says:

      Matthew, You need to be more sophisticated than your answer suggests. Creationists come in as many flavors as evolutionists. Setting aside dishonesty, there are not many well informed propagandists on either side. There are a few worthwhile proponents on each side worth listening to.

      Science will change. It is its very nature. On specific details, and some areas are vastly comprised of technical details, opinions will go back and forth for a while if they are interesting enough.

      The major issues of Creation vs Evolution from my personal inquiry scientifically favor Creation.

      John Smithson, Ph.D., M.S., M.H.C.

  5. rautakyy says:

    I call it the Unintelligent Design. “Nipples for men!” – Evil – in the movie Time Bandits. Creationism seems to be this desperate attempt to andropomorhise the concept of an alledged creator entity, by appointing such a “god” with human motives and morals. Then by these imaginary andropomorphic qualities, like “benevolence” and “reason”, that – in the real world – can not be wittnessed in nature, we should somehow infer there actually exists such a thing as a god (that obviously does not have a direct interrest, or capability to appear to all of us) with caring interrest in our separate individual lives, when no actual evidence of anything as such exists.

    The yolk sac example goes to show, that even by shifting the burden of proof from an extraordinary claim, that a particular god is more than just folklore, we can still conlude, that no evidence of such a god actually exists anywhere.

    • Loved that movie when I was a kid. “Mom! Dad! It’s evil! Don’t touch it!”

    • Anonymous says:

      rautakyy, The problem with your saying there is no evidence for a god, is that you are too self-assured. There has been and is plenty of evidence in my life and in the lives of my friends for a loving benevolent God. You evidently have not met Him yet. What makes you think you can speak for those who have, and for those whose lives have been wonderfully changed because of it?

      And please, don’t be so naive as to think that the “yolk sac” inquiry has been settled. The history of science shows many examples of strongly held ideas by scientists that have been utterly falsified later, unfortunately for some ideas, years later.

      Do some reading beyond evolutionary literature,


      • Barry Lyons says:

        You’re right when you say that science has had a history of getting things wrong. Think of all the things that were once considered sciences but are now considered pseudosciences or dead sciences: alchemy, phrenology, and phlogiston come to mind.

        But Sam Harris ups the ante: “I challenge you to think of a question upon which we had a scientific answer, however inadequate, but for which now the best answer is a religious one.” In other words, Harris is indirectly saying that whenever there HAS been an inadequate answer within the sciences the subsequent better answer still fell—and always falls—within the realm of science. For example, a belief in alchemy gave way to chemistry.

        So do you have a response for Harris? I’ll rephrase his challenge as a question: If the entirety of civilization was lost and we had to rebuild the world, what would we need from religion for that rebuilding? In other words, if we didn’t turn to religion as we rebuilt civilization, we’d be lost without… what, exactly?

  6. Anonymous says:

    First off, before we even start to talk about the broken theory of evolution, we need to figure out how to get something from nothing.

    • When you say “something form nothing,” are you referring to the origin of life, or the origin of matter?

      If LIFE, there are many things we can gain knowledge of without understanding their origins. For example, I wasn’t present for the creation of my car, but I can tell you a lot about it and how it works based on my own observations. If all life has evolved, there are going to be clues (such as empty yolk sacs and useless pseudo-genes), and if all life were designed from scratch, this too might leave clues (such as a wholly unique genetic design for humans). But evolution itself doesn’t attempt to answer the origin (abiogenesis) question, it just explains what happens after “life” begins replicating.

      If MATTER, then see question #6. It may be that matter has always existed (in one form or another), and there is no need to suppose that it once come from nothing (the same argument is used to explain the existence of an eternal God).

      As a creationist, I also used to dismiss evolution because scientists couldn’t prove how life originated. Sure, we can assume God did it, but this isn’t REALLY evidence, it’s just a “God of the gaps” argument, or an “argument from ignorance.” We can’t safely make that assumption until we have some solid evidence. However, if we DO have evidence for evolution, then that certainly goes against the creation model outlined in Genesis, and draws the whole story into question.

      Maybe God created life, maybe life was made probable by a vast and eternal universe, we can’t say. What we CAN honestly say is: “We don’t yet know how life began, but it appears that all life has evolved, or has at least been designed to give the appearance of evolution.”


      • Anonymous says:

        I was referring to mater itself. The second law of thermodynamics can show the Universe had a beginning. The Universe is running out of energy therefore it had to have a start or something to put energy into it. Also it is observed that the Universe is expanding so it had to have a starting point to expand from. That starting point had to have a uncaused first cause (God). If mater never had a beginning it therefore could have never existed. For example, if you rewound time would it rewind to infinity? No. Something had to give the mater energy. As far as evolution, read “Darwin’s Doubt” by Dr. Stephen Meyer. This book was written last year and has mountains of evidence against evolution including evolutions problem with epigenetic information that was discovered in recent years. I am a doubting Thomas but the more I search and ask God to reveal himself to me the more I am reassured that God is the truth and the more it all just makes sense. I don’t quite understand how I can see one thing and others such as yourself see the exact opposite. I’ll look forward to the next post but pray it never comes.

        • The 2nd law of thermodynamics and how it applies to the Universe is still a mystery, but I don’t think it’s an insurmountable one. You’ll recall that the 1st law says that nothing is created or destroyed, so even when our universe winds down, all the matter and energy will STILL exist. So the mystery is “only” how this material finds its way back ’round to doing something else.

          If all matter still exists, I assume gravity will still exist, so perhaps everything will eventually be drawn into one, gigantic, supermassive black hole, like the ones we observe at the center of every galaxy; and maybe the atoms at the center of this dense matter will eventually undergo a change as a result of all that pressure, and trigger another big bang. I’m probably wrong, but there are a lot of theories about how this might work.

          And let’s not forget that 100 years ago we thought ours was the only galaxy, and it wasn’t until 22 years ago that we finally proved ours was not the only planet! For all we know, we may only be one of trillions of universes, we just don’t know.

          But to say, “I don’t know, therefore God,” is just an argument from ignorance. There have been many times throughout history when humans said, “I don’t know, therefore a god, or a demon,” and in every case when the mystery was solved there was a natural explanation. Based on those experiences, I would expect that this mystery (if solved) would probably end the same way.

          How matter manages to find its way ’round to another big bang is trivial mystery compared to explaining god. Explaining God requires so much more, like explaining how someone can be made OF NOTHING… yet still be something. (And if God IS made of something — anything — where did this substance come from? Did it always exist? Was God just the first thing to evolve?) We also need to explain how this nothing-man can ALWAYS exist, and what it means to live an infinite life outside of time. How does he exist without any energy to sustain him or his thoughts? And how he can create matter and energy… from nothing. Even if God CAN do this, HOW does he do it? Is it magic? Can he teach someone else how to do it? Or has this stuff just always existed?

          Given the two choices, God is a much more difficult mystery to explain.

          I’m familiar with Stephen Meyer. I believe that epigenetic information is, again, one of those cases where ID proponents try to say “God did it!” and then science finds a natural explanation (http://www.sciencedaily.com/releases/2013/01/130124150808.htm). The same thing happened with the bacterial flagellum, and the eye. New and mysterious discoveries always seem to attract attention from fringe groups trying to prove their point (it happens so often with quantum physics that their explanations became known as “quantum flapdoodle”).

          Anyway, not sure how we went from human yolk sacs to the origin of the universe, but glad your asking questions and looking into both sides of the argument (keeps one from becoming too biased).

          Take care,

          • It is oxymoronic to suggest the very incredible concept of a miraculous, ever-existing, complex God as the explanation for the relatively less incredible mystery of the existence of our universe and life.

            I always say that using God to explain the origin of the universe and life, is analogous to someone borrowing 1,000,000 dollars to pay off a 100 dollar debt.

        • DanD says:

          If you are going to argue that god could exist before the big bang, then you also have to accept that something else which was capable of creating the big bang could have as well.

          As far as Mr. Meyer’s long form strawman argument, he does the usual. He constructs an argument he can oppose, and argues against it, instead of understanding that science continues to move forward, explaining puzzles as it goes.

        • Maroo says:

          I would suggest that when it comes to the realm of particle physics, one not pay too much attention to the Laws of Thermodynamics. There is a LOT of strange stuff that happens at that level, including definitions of the word “nothing” that really mean “something” (or at least that is how it kinda seems to me). In the realm of particle physics, which is the realm one is talking about when it comes to the start of our universe, the statement “One can’t get nothing from something” simply doesn’t mean anything anymore. Particle physicists say we get “something” from “nothing” all the time. That being said, the descriptions of what happened in the first second or so after the Big Bang sound strikingly like the descriptions of what would likely happen after a super massive black hole becomes unstable or “explodes”. Whether an exploding black hole was “in” our universe obliterating everything that was there before it or whether an exploding black hole was in a separate universe, maybe a different part of our multiverse, somehow causing our universe to “start”, or any of the other theoretical ideas floating around about this are all so very, very fascinating. Not only is no external intelligence required for the start of our universe, but the other ideas for how our universe started are such more interesting ones, I don’t understand how anyone wouldn’t think, “this is so cool, let’s find out more”.

      • Anonymous says:

        Your vague conjecture doesn’t help the controversy. The Intelligent Design proposal (from its major spokespersons) is very explicit in its claims for evidence of a designer from information science and from specific sciences like forensics, archaeology, S.E.T.I., and engineering.

        You say that it “appears that all life has evolved”. Wrong, the truth is that life appears to have been designed. Francis Crick (co-discoverer of the structure of DNA) said that scientists have to keep reminding themselves that life wasn’t designed. That’s how strong the common sense view of things points to creation and design. So you have to brain-wash yourself to overcome everyday observations, says Francis Crick. The information system of the DNA is a major problem for evolutionists. Information has never been observed to have any other source than from a mind, an intelligent agent.

        Do some reading that will help you break out of the evolutionary assumptions,

        John Smithson, Ph.D.

        • Hi John,

          “Information has never been observed to have any other source than from a mind, an intelligent agent.”

          I don’t believe this to be true — even snowflakes contain a certain amount of naturally-occurring repeating information, as do crystals, RNA, and other molecular structures.

          But if we assume that all information demands an intelligent designer, then we must also assume that the intelligent designer himself required a designer (and to deny this would be special pleading). If we should then try to back out of our own original assertion and insist that God’s complexity and information can exist without an intelligent agent, then we must also admit that it’s possible for other complex things to arise without any intelligent cause.

          If information is impossible without an intelligent agent, then it is impossible for God to exist without one. But if the complexity that is God can exist without a designer, then the complexity that is DNA can also exist without a designer.

          We either have an infinite string of more and more complex designers without cause, or we have a universe with little complex information, which occasionally gives rise to complex things through sheer probability and selection. It seems to me the latter would be the more reasonable proposition.


  7. gil says:

    hi 500 q. here is simple senario: the vitalin gene swich on and off during development. so the stop codon swich it of. the human beta globin also sitch on and off:


    The arrangement of the genes directly reflects the temporal differentiation of their expression during development, with the early-embryonic stage version of the gene located closest to the LCR. If the genes are rearranged, the gene products are expressed at improper stages of development.

    Expression of these genes is regulated in embryonic erythropoiesis by many transcription factors, including KLF1,[2] which is associated with the upregulation of adult haemoglobin in adult definitive erythrocytes, and KLF2,[3] which is vital to the expression of embryonic hemoglobin.

    • Anonymous says:

      Thank you, gil, but this does not help the discussion for most people. You offer no conclusion that relates to our apparent main topic.

      Nevertheless, be in God’s care,


  8. Think_Logically says:

    Interesting how creationists are so willing to speculate regarding this or that possible explanation that has zero basis in fact, yet are so quick to reject any finding anchored to reason and logic. Superstition is tricky business. —— “I’ll believe anything this book states, no matter how far-fetched, but if I can test it myself it must be incorrect.” Brilliant!

  9. guy says:

    what if we will see a self replicating robot ( lets say even with dna)on a far planet?. do we need to conclude design or a natural process in this case? remember that according to evolution if its made from organic components and have a self replicating system we need to conclude a natural process. but we know that evne a self replicating robot is evidence for design. so the burdon of proof is on the evolution side in this case

    evolutionists claiming that small steps in milions of years will create a big steps. but according to this a lots of small steps in self replicat car (with dna) will change into an airplan.

    but there is no step wise from car into an airplane. so its impossible actually to change one kind into another.

    evolutionist claim that common similarity is evidence for common descent. but according to this if we will see 2 similar (self replicating or not) cars we will need to conclude that they evolved from each other and not made by a designer. but we know that this similarity is evidence for a shared designer and not a shared descent

    • Barry Lyons says:

      Your response is incoherent. In particular, your use of the word “kind” gives away the game: “kind” is a word that is found in Genesis, and it’s a word that isn’t used by evolutionary biologists. Also, there’s your bizarre attempt at making a comparison of the development of man-made objects (cars and planes) with replicating organisms.

      The burden of proof for evolution has been met. I’ll let Jerry Coyne explain (from an interview):

      “Nobody worships Darwin as a religion. We don’t adhere to a set of dogmas that are unchanging and unquestionable. We all recognize that Darwin was wrong about a lot of stuff. His theories of genetics were wrong, his theories of biography were wrong—that’s been corrected by plate tectonics—his stuff on sexual selection is very good but not complete. Evolutionary biology is constantly changing and revising its conclusions. But the main conclusions that Darwin made—that evolution occurred, that it occurred through natural selection, that there was common ancestry and splitting and that it happened slowly—those have all been supported. We accept those things because mountains of evidence have shown them to be true.”

      To say evolution is NOT true is to take another position of which there can only be two: a) nobody has a clue as to how life flourishes and propagates or b) all life on Earth was created in a few days’ time (according to a certain book) and that since this “creation” all life has remained “static” and unchanging. The burden of proof rests with you to demonstrate the validity of the latter view. You will fail in your endeavor to come up with some evidence for it. Everyone has failed in this endeavor because there is simply no evidence that all life popped into existence on the whim of some Supernatural Being.

    • Hi Guy!

      I think we’d need to gather a lot of information about these unique self-replicating robot-cars before we could speculate about their origins.

      “But there is no step wise from car into an airplane. so its impossible actually to change one kind into another.”

      Again, I’m not sure how this process works with theoretical “robot cars with DNA”, but with evolution, “cars” never set out to become “airplanes.” Still, it can happen.

      Take the squirrel for example. It is not trying to become a flying animal, but we do have some “flying” squirrels. At some point, a genetic difference provided for one (or more) squirrels to have excess skin between it’s limbs. This minor advantage allowed these squirrels to soar further and land safer than those without (which died). Over time, more and more exaggerated flaps resulted in greater advantages, and the trend continued. Female squirrels may have even begun to favor mates with larger flaps (because what girl can resist big flaps, lol).

      Anyways… if the trend continues, there may one day exist lighter-weight squirrels that soar further, or squirrels that flap their arms to gain even greater distance. They could end up like bats or pteranodons, which fully developed the ability to fly. These animals were not “designed” to fly, but small changes led to big changes, and these “cars” essentially became “planes.”

      But what about a change in “kinds”?

      It’s only creationists who are caught up on the word “kind.” Creationists want the Bible to remain true, so they look to refute any change in “kind”. But the Bible doesn’t define “kind,” or at which point one “kind” becomes another.

      But archaeopteryx, for example, exhibits features of both birds and reptiles: it’s between two kinds. And recent discoveries have shown that chickens can still be made to exhibit primitive features from their dinosaur ancestors by making minor changes to their DNA. (See : http://www.bbc.com/earth/story/20150512-bird-grows-face-of-dinosaur). They can even be made to grow teeth (see: https://www.nature.com/scitable/topicpage/atavism-embryology-development-and-evolution-843). So which kind is it?

      One scientist has suggested recreating a dinosaur by reverse-engineering chickens to a more primitive state. Assuming this were possible, at which point would does it cease to be one “kind,” and start being another? (Or does the creationist then insist they must’ve always been the same kind? )

      But technically, a car may never become a plane, just as a dog may never become a cat. But if you go back far enough, you can find their common ancestor.

      But to get to the heart of your point, if the similarities in the DNA of all animals are indicative of a common designer, and not common descent, we should expect to see God reusing his more elaborate designs across the different “kinds” (see question #48). God should be putting crab arms on bears, and bird wings on squirrels. A designer would not need to reinvent wings with each new species. A designer — who is clearly reusing DNA just to save time — will cut and paste good designs between species, but evolution is forced to reinvent the wheel every time, and this is what we observe happening.

      Thanks for the question,

  10. J K says:

    Hi 500Q,
    I don’t understand the flow of the argument here. Evolution proposes that humans descended from animals that had and needed active yolk-related genes. Obviously, this begs the question that according to that theory, humans should still have these genes active, which they don’t. The solution proposed is that at some point in mammalian history, these genes became unnecessary, and that allowed them to be shut off without consequence–once we could ingest the necessary nutrients, we didn’t need to make them ourselves. But wouldn’t it be helpful to have, still? I mean, the most logical thing is to simply regulate it (like a million other production pathways in our bodies), not for it to become completely inactivated! To me, survival of the fittest should have preserved our ability to produce necessary nutrients whenever they are necessary (such as famine, etc.)

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