You seem extremely confused again now. Nobody disputes that there are many examples of systems where one thing A depends on another thing B to function. What they are disputing is that this co-dependence relationship means the A+B system cannot evolve.
But we know that such relationships can evolve. We know examples where A has some ancestor from which A evolved, and B has some ancestor from which B evolved, and that they then later became dependent on each other to function.
For example this:
Abstract
Many cellular processes are carried out by molecular ‘machines’— assemblies of multiple differentiated proteins that physically interact to execute biological functions1–8. Despite much speculation, strong evidence of the mechanisms by which these assemblies evolved is lacking. Here we use ancestral gene resurrection9–11and manipulative genetic experiments to determine how the complexity of an essential molecular machine—the hexameric transmembrane ring of the eukaryotic V-ATPase proton pump—increased hundreds of millions of years ago. We show that the ring of Fungi, which is composed of three paralogous proteins, evolved from a more ancient two-paralogue complex because of a gene duplication that was followed by loss in each daughter copy of specific interfaces by which it interacts with other ring proteins. These losses were complementary, so both copies became obligate components with restricted spatial roles in the complex. Reintroducing a single historical mutation from each paralogue lineage into the resurrected ancestral proteins is sufficient to recapitulate their asymmetric degeneration and trigger the requirement for the more elaborate three-component ring. Our experiments show that increased complexity in an essential molecular machine evolved because of simple, high-probability evolutionary processes, without the apparent evolution of novel functions. They point to a plausible mechanism for the evolution of complexity in other multi-paralogue protein complexes.
And this:
https://www.pnas.org/content/118/7/e2018731118.short
Significance
Human muscle-type acetylcholine receptors are heteropentameric ion channels formed from four evolutionarily related subunits, which assemble with a specific stoichiometry and arrangement. It has long been thought that each of the modern-day subunits are required for function. We dispel this notion by first showing that an ancestral β-subunit can replace both the β- and δ-subunits in human acetylcholine receptors. We then identify a single historical amino acid substitution that eliminates the ability of the ancestral β-subunit to functionally replace the human δ-subunit. Our work experimentally demonstrates how acetylcholine receptor subunit complexity could have evolved and uncovers a form of contingency that is unique to heteromeric protein complexes, in which mutations that “lock in” individual subunits determine future evolutionary paths.
Abstract
Human adult muscle-type acetylcholine receptors are heteropentameric ion channels formed from four different, but evolutionarily related, subunits. These subunits assemble with a precise stoichiometry and arrangement such that two chemically distinct agonist-binding sites are formed between specific subunit pairs. How this subunit complexity evolved and became entrenched is unclear. Here we show that a single historical amino acid substitution is able to constrain the subunit stoichiometry of functional acetylcholine receptors. Using a combination of ancestral sequence reconstruction, single-channel electrophysiology, and concatenated subunits, we reveal that an ancestral β-subunit can not only replace the extant β-subunit but can also supplant the neighboring δ-subunit. By forward evolving the ancestral β-subunit with a single amino acid substitution, we restore the requirement for a δ-subunit for functional channels. These findings reveal that a single historical substitution necessitates an increase in acetylcholine receptor complexity and, more generally, that simple stepwise mutations can drive subunit entrenchment in this model heteromeric protein.
And many others, such as the evolution of increased complexity in hemoglobin also discussed on this website not long ago.
So this is actually the reality.