From Newsgroup: talk.origins

longish

https://archive.is/ffTZ1

How Did Hands Evolve? The Answer Is Behind You.

The evolutionary blueprint for hands was
borrowed in part from a much older genetic
plan for our nether regions, a new study
suggests.

...
Now the precise DNA-editing technology known as CRISPR is letting
scientists reconstruct this ancient evolutionary change in molecular
detail. It turns out that hands and feet were not the products of new
genes doing new things. Rather, through natural selection, pieces of old genetic recipes for ancient body parts were cobbled together into new combinations.
...
On Wednesday, Dr. Hintermann and her colleagues showed just how old some
of those pieces were: The recipe for building hands was borrowed in part
from the one for our nether regions.

Dr. Hintermann and her colleagues carried out their study by tracing the activity of genes in developing embryos.

Scientists have identified some of the locks that enable embryos of
humans and other species to grow limbs. In 2011, Denis Duboule, a
biologist at the University of Geneva, and his colleagues discovered a half-dozen molecular locks sitting side-by-side along a stretch of DNA
called 5DOM. When 5DOM was snipped out of a mouse embryorCOs DNA, the
embryo grew legs but failed to grow feet.

Dr. Duboule and his colleagues wondered how this crucial set of locks
evolved. Did it arise when our ancestors first came ashore and evolved
limbs? Or did it exist earlier, in our finned ancestors?

To tackle that question, Christopher Bolt, then a graduate student in
Dr. DuboulerCOs lab, searched through the genome of the zebrafish. He discovered that it, too, had 5DOM.

Zebrafish and mammals share an ancient common ancestor that lived more
than 400 million years ago. The Geneva teamrCOs discovery suggested that
this primordial ancestor already had 5DOM. And if it was still intact in zebrafish, it must be doing something in their embryos. rCLIt could not be there by chance,rCY Dr. Hintermann said.

Dr. Hintermann, who took over the project while working in the Geneva
lab, grew zebrafish embryos from which she had removed the 5DOM locks,
using CRISPR. If the locks were important in the development of fish
fins, then deleting them might reveal how.

To her surprise, deleting 5DOM had little effect on the developing fins.
But it disrupted a region on the underside of the zebrafishrCOs tail,
where there are two openings: the anus, and a hole for the bladder and
for sexual organs.

This surprise prompted the researchers to take a closer look at the same region in mouse embryos. Here they got a second surprise: 5DOM unlocks
the genes that built that region in mammals, too.

These and other experiments led the scientists to a new hypothesis for
the evolution of fingers and toes. The story starts a half-billion years
ago, with the earliest, simplest fish. Their bodies were little more
than heads connected to long-ribbon-like bodies; they swallowed food,
which made its way down a long digestive tract until the remnants
escaped through the anus. A nearby opening was used for sex, and the
release of urine.

The embryos of this protofish unlocked different genes to create the
different parts of its body. At the far end, 5DOM unlocked the genes for
the anus as well as the opening for its urethra and sexual organs.

That genetic recipe hasnrCOt changed in a half-billion years. ThatrCOs why 5DOM still controls the development of that region in both zebrafish and
mice rCo and us.

But about 360 million years ago, the scientists propose, 5DOM underwent
an evolutionary change. Now it could build not only our nether regions
but our fingers and toes, too.

Hands and nether parts might seem to have little in common, but there
are some key similarities. For one thing, both are extremities: In early
fish, 5DOM unlocked genes that determined the anatomy at the far end of
the body. In a developing limb, the fingers and toes develop at the far
end, too.

But Neil Shubin, an evolutionary biologist at the University of Chicago
and another author of the study, said that the precise evolutionary
changes that had given 5DOM its new job remain a mystery.

--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: talk.origins

On 9/23/2025 4:46 PM, Pro Plyd wrote:

longish

https://archive.is/ffTZ1

How Did Hands Evolve? The Answer Is Behind You.

The evolutionary blueprint for hands was
borrowed in part from a much older genetic
plan for our nether regions, a new study
suggests.

...
Now the precise DNA-editing technology known as CRISPR is letting
scientists reconstruct this ancient evolutionary change in molecular
detail. It turns out that hands and feet were not the products of new
genes doing new things. Rather, through natural selection, pieces of old genetic recipes for ancient body parts were cobbled together into new combinations.
...
On Wednesday, Dr. Hintermann and her colleagues showed just how old some
of those pieces were: The recipe for building hands was borrowed in part from the one for our nether regions.

Dr. Hintermann and her colleagues carried out their study by tracing the activity of genes in developing embryos.

Scientists have identified some of the locks that enable embryos of
humans and other species to grow limbs. In 2011, Denis Duboule, a
biologist at the University of Geneva, and his colleagues discovered a half-dozen molecular locks sitting side-by-side along a stretch of DNA called 5DOM. When 5DOM was snipped out of a mouse embryorCOs DNA, the
embryo grew legs but failed to grow feet.

Dr. Duboule and his colleagues wondered how this crucial set of locks evolved. Did it arise when our ancestors first came ashore and evolved limbs? Or did it exist earlier, in our finned ancestors?

To tackle that question, Christopher Bolt, then a graduate student in
Dr. DuboulerCOs lab, searched through the genome of the zebrafish. He discovered that it, too, had 5DOM.

Zebrafish and mammals share an ancient common ancestor that lived more
than 400 million years ago. The Geneva teamrCOs discovery suggested that this primordial ancestor already had 5DOM. And if it was still intact in zebrafish, it must be doing something in their embryos. rCLIt could not be there by chance,rCY Dr. Hintermann said.

Dr. Hintermann, who took over the project while working in the Geneva
lab, grew zebrafish embryos from which she had removed the 5DOM locks,
using CRISPR. If the locks were important in the development of fish
fins, then deleting them might reveal how.

To her surprise, deleting 5DOM had little effect on the developing fins.
But it disrupted a region on the underside of the zebrafishrCOs tail,
where there are two openings: the anus, and a hole for the bladder and
for sexual organs.

This surprise prompted the researchers to take a closer look at the same region in mouse embryos. Here they got a second surprise: 5DOM unlocks
the genes that built that region in mammals, too.

These and other experiments led the scientists to a new hypothesis for
the evolution of fingers and toes. The story starts a half-billion years ago, with the earliest, simplest fish. Their bodies were little more
than heads connected to long-ribbon-like bodies; they swallowed food,
which made its way down a long digestive tract until the remnants
escaped through the anus. A nearby opening was used for sex, and the
release of urine.

The embryos of this protofish unlocked different genes to create the different parts of its body. At the far end, 5DOM unlocked the genes for
the anus as well as the opening for its urethra and sexual organs.

That genetic recipe hasnrCOt changed in a half-billion years. ThatrCOs why 5DOM still controls the development of that region in both zebrafish and mice rCo and us.

But about 360 million years ago, the scientists propose, 5DOM underwent
an evolutionary change. Now it could build not only our nether regions
but our fingers and toes, too.

Hands and nether parts might seem to have little in common, but there
are some key similarities. For one thing, both are extremities: In early fish, 5DOM unlocked genes that determined the anatomy at the far end of
the body. In a developing limb, the fingers and toes develop at the far
end, too.

But Neil Shubin, an evolutionary biologist at the University of Chicago
and another author of the study, said that the precise evolutionary
changes that had given 5DOM its new job remain a mystery.

Deuterostomes (vertebrates) have embryos that develop a blastopore that becomes the anus and the embryo proceeds to differentiate to the mouth
in order to form a tubular lifeform with an anus and mouth. Protostome embryos have the blastopore develop into the mouth and differentiate the embryo to the anus. So the sequential use of the same regulators
follows normal deuterostome development.

Ron Okimoto

--- Synchronet 3.21a-Linux NewsLink 1.2