Posted on 12/01/2021 10:27:56 AM PST by Heartlander
Recently, the sci-fi dream of self-replicating robots has been in the news, thanks to the University of Vermont, Tufts University, and the Wyss Institute for Biologically Inspired Engineering at Harvard. A recent experiment with frog cells was hailed by news outlets as disparate as CNN (“World’s first living robots can now reproduce, scientists say”) and Daily Wire (“American Universities Create First ‘Self-Replicating Living Robots’”). And it was also debunked by Ars Technica: (“Interesting research, but no, we don’t have living, reproducing robots”).
So what’s really happening?
Self-replication is a very tricky problem of information. To truly self-replicate, an organism must completely copy the information necessary for function. Seems simple enough but it introduces a conundrum. For the organism to copy its information, it must also copy the ability to copy its information. Solving this problem of self-reference is very difficult.
The easiest realm in which we can solve the problem of self-reproduction so far is computer code. John von Neumann (1903–1957), one of the inventors of the modern computer, designed a self-replicator known as the Von Neumann Universal Constructor. The Constructor is a genius piece of insight, anticipating the discovery of naturally self-reproducing code in DNA.
However, this is not the same scenario with the xenobots that are making the news. They are robots in only the loosest sense of the word. The term “robot” refers to a complex mechanical and computational entity that engineers have carefully crafted. These xenobots are actually stem cells from an African frog (Xenopus laevis):
The biologists, Douglas Blackiston et al., did not create the stem cells. The stem cells already showed self-reproducing behavior, as is the nature of stem cells. The biologists contributed only the fact that a computer cranked through many configurations of these stem cells to find one that was a bit better at self-reproduction — and not very much better.
Calling these cells “self-reproducing robots” is like saying that humans create catbots when a pet cat produces a litter of kittens.
To add glitz to the paper, the researchers claimed to use an “evolutionary algorithm” to do the cranking. But the algorithm is not really evolution as we know it. The algorithm picks the best members from a set of randomly generated configurations and then further randomly varies each individual member.
Thus. the evolutionary algorithm assumes that self-reproduction already exists and that there is no genetic crossover or survival of the fittest via competition for resources. The only way in which the algorithm is like evolution is that it includes an element of random variation and selection — but the selection is for a predefined goal. It does not arise naturally from the algorithm itself.
However, the biggest assumption in the algorithm is that all the machinery that does the hard work, the stem cell, already exists within a simulation that the algorithm uses to evaluate each configuration. So, even though the use of the term “evolution” makes it seem that the researchers generated self-reproducing cells through the use of evolution, their work is not at all like the conventional biological model of evolution, which is upposed to start with nothing and have no designer picking the likely winners.
All in all, the research was reported in a manner that implies that the scientists had discovered a plausible way self-reproduction can evolve. While their work is a very clever achievement, the paper does not provide a plausible path for self-reproduction, nor do the jury-rigged organisms on display actually self-replicate.
Given what Boston Dynamics has achieved so far, I hope not, either.
They “programmed” this thing to potentially replicate itself by how they manually stacked the skin and muscle stem cells together.
Maybe I’ve never figured out the right terminology for this question, but basically I’ve so far not found a good answer for where is the master plan for a multi-cellular organism stored and how does it get implemented? DNA is the code for individual cells and all their amazing internal machinery, and we are told that certain genes in the DNA are activated or deactivated to make the cell specialized for a certain function, during differentiation.
The books say this particular gene turns on and another particular gene turns off to make a liver cell versus a lung cell, but I’ve never been able to pin down where the master plan for all this differentiation is stored, and how does it implement itself?
Even if you assume “it’s in the DNA” the mystery remains because all cells get the same DNA. What makes a future lung cell in the embryo express a certain subset of genes in the DNA, while a future liver cell expresses a different subset of genes? And how do they arrange themselves into complex structures?
The implementation part seems to be a function of Wnt proteins. The article below is hinting, Wnt proteins and other chemical signals have to be pre-existing prior to first cell division (since there are receptors on the stem cell) and influence how the cell develops/matures. It seems it’s the chemical signals that form the cell into a specialized form, while Wnt keeps it dividing until matured.
Maybe ‘the code’ is out there waiting to be discovered. But what if ‘The code’ is a transient artifact? a ‘spark’ but not a lasting fire? Could it lie inside the mechanisms of the combining of two sexed DNA strands or some happening in the ovum or sperm’s proteins during the fertilization process that leads to triggering the production of those proteins and chemical signals in anticipation of stem cell division (the old, ‘spark of life’)? And then discarded and resorbed as waste along with the first discarded differentiation divisions and simply not to be seen in a mature cell?
” the loss of the Wnt3a signal is known to cause cultured stem cells to begin differentiating... One of the daughters is always closer and remains pluripotent. The other is further from that signal; it begins to differentiate.”
some cell programming ‘signals’
https://www.tocris.com/cell-biology/stem-cell-reprogramming
Whatever form the multi-cellular code (the grand scheme of the organism) takes, it is preserved and it is passed along in sperm and egg, we know that much.
There is a higher order of order in DNA called DNA origami. It’s a very intricate folding pattern which forms transcription loops for RNA messaging.
Imagine how densely and intricately a two-meter length of human DNA must be folded to fit into a single cell nucleus. The folding pattern might contain a template for the multi-cellular organism, such that any differentiated cell would have a built-in road map of where it fits into the grand scheme of the organism.
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