From: me22over7@gmail.com   
      
   On 30/12/2025 3:55 pm, MarkE wrote:   
   > On 30/12/2025 1:49 pm, David Canzi wrote:   
   >> On 12/27/25 06:27, MarkE wrote:   
   >>> On 24/12/2025 7:27 am, John Harshman wrote:   
   >>>> You're just avoiding the question, which I will repeat:   
   >>>>   
   >>>> But how many genetic changes do you think were necessary to turn the   
   >>>> human-chimp ancestor into a modern human? Give me a ballpark.   
   >>>>   
   >>>   
   >>> Much more than "a few thousand", i.e. orders of magnitude.   
   >>   
   >> Can you say something actually quantitative, ie. something of the   
   >> form x plus or minus y percent, and if you do this, can you show   
   >> how you calculated it?   
   >>   
   >> It's your job to justify your claim.  If you haven't made the effort   
   >> to justify your claim, nobody owes you the effort to justify their   
   >> non-agreement with your claim.  You're freeloading.   
   >>   
   >   
   > I acknowledge that I can't put a number on it. Partly because of a lack   
   > of expertise/ability, and partly because, well, who can? But that does   
   > not mean it doesn't exist.   
   >   
   > See my more recent post "The information problem", where I attempt to   
   > grapple with this some more.   
   >   
   > I think it's a fascinating area, even setting aside the creation/   
   > evolution arguments. A single fertilised egg dividing and exponentially   
   > multiplying to create an new and unique human should always astonish us,   
   > no matter how much we may understand the processes involved.   
   >   
   > What do you think?   
   >   
   > _______   
   >   
   >   
   > FROM ONE CELL TO A HUMAN BEING: AN OVERVIEW OF THE PROCESS AND ITS   
   > MYSTERIES   
   >   
   > *Fertilisation* begins when a sperm and ovum fuse to form a single cell:   
   > the *zygote*. In that moment, a new, genetically unique human organism   
   > exists. Yet nothing visible distinguishes this cell from countless   
   > others. What follows is one of the most extraordinary processes known in   
   > nature.   
   >   
   > ---   
   >   
   > ## 1. Exponential division without growth: cleavage   
   >   
   > Within hours, the zygote begins dividing: 1 cell becomes 2, then 4, 8,   
   > 16, and so on. These early divisions, called *cleavage*, are remarkable   
   > because the total size of the embryo does not increase. Instead, the   
   > original cytoplasm is partitioned into ever-smaller cells.   
   >   
   > Key features:   
   >   
   > * Division is rapid and tightly synchronized.   
   > * Cells remain enclosed in the original outer membrane.   
   > * The embryo reaches ~100 cells in a few days.   
   >   
   > *What is striking:*   
   > All cells initially appear equivalent, yet they are already on   
   > trajectories that will lead to radically different fates.   
   >   
   > *What we do not fully understand:*   
   > How early asymmetries—subtle differences in molecular concentrations,   
   > mechanics, and timing—bias later cell fate decisions with such reliability.   
   >   
   > ---   
   >   
   > ## 2. Self-organisation and implantation: the blastocyst   
   >   
   > After several days, the embryo reorganises into a *blastocyst*—a hollow   
   > structure with:   
   >   
   > * an *inner cell mass* (which will become the body),   
   > * and an *outer layer* (which will help form the placenta).   
   >   
   > The blastocyst implants into the uterine wall, establishing a   
   > biochemical dialogue with the mother that allows pregnancy to continue.   
   >   
   > *What is striking:*   
   > This organisation emerges without a central controller. Cells “decide”   
   > their roles through local interactions, gene regulation, and physical   
   > constraints.   
   >   
   > *What we do not fully understand:*   
   > How global structure arises so robustly from local rules, and why   
   > implantation succeeds or fails so often despite apparently normal embryos.   
   >   
   > ---   
   >   
   > ## 3. The body plan appears: gastrulation   
   >   
   > Around the third week, the embryo undergoes *gastrulation*, often called   
   > *the most important event in your life*. A simple sheet of cells folds   
   > and rearranges to form three foundational layers:   
   >   
   > * *Ectoderm* → nervous system, skin   
   > * *Mesoderm* → muscle, bone, blood, heart   
   > * *Endoderm* → gut, liver, lungs   
   >   
   >  From this point onward, the basic body axes—head to tail, back to   
   > front, left to right—are established.   
   >   
   > *What is striking:*   
   > A consistent human body plan emerges from dramatic cellular movements   
   > that look, under a microscope, almost chaotic.   
   >   
   > *What we do not fully understand:*   
   > How genetic instructions, chemical gradients, and mechanical forces are   
   > integrated in real time to yield precise, repeatable anatomy.   
   >   
   > ---   
   >   
   > ## 4. Differentiation and organ formation: organogenesis   
   >   
   > Cells now differentiate into hundreds of specialised types and assemble   
   > into organs. Neural cells wire themselves into circuits. Blood vessels   
   > branch through tissues. The heart begins beating while still forming.   
   >   
   > Cell numbers increase exponentially, eventually reaching *tens of   
   > trillions*, yet:   
   >   
   > * proportions are maintained,   
   > * left–right symmetry is mostly preserved,   
   > * errors are detected and corrected.   
   >   
   > *What is striking:*   
   > No cell “knows” the whole plan, yet the whole plan reliably appears.   
   >   
   > *What we do not fully understand:*   
   >   
   > * How large-scale structures (like vascular trees or neural   
   > connectivity) are specified without explicit blueprints   
   > * How errors are corrected without derailing development   
   > * How timing is coordinated across vastly different scales   
   >   
   > ---   
   >   
      
   [continued in next message]   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)