I will praise thee; for I am fearfully and wonderfully made. Psalm 139:14
"We’ve just discovered a new part of the brain’s waste disposal system (New Scientist, 5 Jan 2023). Reporter Clare Wilson uses the “royal we” in this Tontological headline, but she didn’t discover this: scientists at the University of Rochester and University of Copenhagen did.
A new anatomical structure has been discovered that is part of the brain’s waste disposal system.The tissue is a thin membrane encasing the brain that keeps newly made cerebrospinal fluid – which circulates inside the brain – separate from “dirty” fluid containing cells’ waste products.It was already known that there are three membranes between the skull and the brain. The new structure is a fourth membrane, lying on top of the innermost membrane, called the subarachnoid lymphatic-like membrane (SLYM). It is extremely thin, with a width of just a few cells or, in places, even one cell.
---It had not been discovered previously, because it disintegrates when
the skull is opened up, and is not visible in imaging techniques. The
scientists found it in studies on mice, and figured out what it was
doing.
Newly Discovered Anatomy Shields and Monitors Brain (University of Rochester Medical Center,
5 Jan 2023). This press release from one of the institutions
discovering the SLYM tells more about it. The membrane is certainly
“slim” as the name implies, but it serves important functions:
The new membrane is very thin and delicate, consisting of only a 
few cells in thickness. Yet SLYM is a tight barrier, allowing only very small molecules to transit and it also seems to separate “clean” and “dirty” CSF. This last observation hints at the likely role played by SLYM in the glymphatic system, which requires a controlled flow and exchange of CSF, allowing the influx of fresh CSF while flushing the toxic proteins associated with Alzheimer’s and other neurological diseases from the central nervous system .
The paper about this was published in Science on 5 Jan 2023. The Abstract says:
The central nervous system is lined by meninges, classically known as dura, arachnoid, and pia mater. We show the existence of a fourth meningeal layer that compartmentalizes the subarachnoid space in the mouse and human brain, designated the subarachnoid lymphatic-like membrane (SLYM). SLYM is morpho- and immunophenotypically similar to the mesothelial membrane lining of peripheral organs and body cavities, and it encases blood vessels and harbors immune cells. Functionally, the close apposition of SLYM with the endothelial lining of the meningeal venous sinus permits direct exchange of small solutes between cerebrospinal fluid and venous blood, thus representing the mouse equivalent of the arachnoid granulations. The functional characterization of SLYM provides fundamental insights into brain immune barriers and fluid transport.
There is no mention in the paper of how this system might have evolved.
The Creator thought of everything. Let’s give credit where credit is due." CEH