Evolution has adapted the digits of mammals for an enormous range of uses, from our opposable thumbs to the spindly digits that support bat wings to the robust bones that support the hoofs of horses. But how we got digits in the first place hasn't been entirely clear. The fish that limbed vertebrates evolved from don't have obvious digit equivalents, and the most common types of fish just have a large collection of rays supporting their fins.

Despite this uncertainty, we have identified some genes that seem to be essential for both digit formation and the development of rays in the fins of fish, suggesting that there are parallels between the two. But a new study suggests that these parallels are a bit of an accident, and digits come by re-deploying a genetic network that controls a completely different process: the formation of the cloaca, a single organ that handles all of the fish's excretion.

Hox genes and digits

One of the key regulators of limb development is a set of genes called homeobox proteins, which attach to DNA and regulate the activity of nearby genes. In animals, many of these homeobox, or hox genes, are formed into clusters. Mammals have four clusters of hox genes, each of which encodes roughly 10 individual homeobox proteins. The cluster helps to organize where the hox genes are active, with the genes at one end of the cluster being active at the front of an embryo, and those at the other end active at the tail.

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Evolution has adapted the digits of mammals for an enormous range of uses, from our opposable thumbs to the spindly digits that support bat wings to the robust bones that support the hoofs of horses. But how we got digits in the first place hasn't been entirely clear. The fish that limbed vertebrates evolved from don't have obvious digit equivalents, and the most common types of fish just have a large collection of rays supporting their fins.

Despite this uncertainty, we have identified some genes that seem to be essential for both digit formation and the development of rays in the fins of fish, suggesting that there are parallels between the two. But a new study suggests that these parallels are a bit of an accident, and digits come by re-deploying a genetic network that controls a completely different process: the formation of the cloaca, a single organ that handles all of the fish's excretion.

Hox genes and digits

One of the key regulators of limb development is a set of genes called homeobox proteins, which attach to DNA and regulate the activity of nearby genes. In animals, many of these homeobox, or hox genes, are formed into clusters. Mammals have four clusters of hox genes, each of which encodes roughly 10 individual homeobox proteins. The cluster helps to organize where the hox genes are active, with the genes at one end of the cluster being active at the front of an embryo, and those at the other end active at the tail.

Read full article

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Evolution has adapted the digits of mammals for an enormous range of uses, from our opposable thumbs to the spindly digits that support bat wings to the robust bones that support the hoofs of horses. But how we got digits in the first place hasn't been entirely clear. The fish that limbed vertebrates evolved from don't have obvious digit equivalents, and the most common types of fish just have a large collection of rays supporting their fins.

Despite this uncertainty, we have identified some genes that seem to be essential for both digit formation and the development of rays in the fins of fish, suggesting that there are parallels between the two. But a new study suggests that these parallels are a bit of an accident, and digits come by re-deploying a genetic network that controls a completely different process: the formation of the cloaca, a single organ that handles all of the fish's excretion.

Hox genes and digits

One of the key regulators of limb development is a set of genes called homeobox proteins, which attach to DNA and regulate the activity of nearby genes. In animals, many of these homeobox, or hox genes, are formed into clusters. Mammals have four clusters of hox genes, each of which encodes roughly 10 individual homeobox proteins. The cluster helps to organize where the hox genes are active, with the genes at one end of the cluster being active at the front of an embryo, and those at the other end active at the tail.

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Anthropic's AI models could potentially help spies analyze classified documents, but the company draws the line at domestic surveillance. That restriction is reportedly making the Trump administration angry.

On Tuesday, Semafor reported that Anthropic faces growing hostility from the Trump administration over the AI company's restrictions on law enforcement uses of its Claude models. Two senior White House officials told the outlet that federal contractors working with agencies like the FBI and Secret Service have run into roadblocks when attempting to use Claude for surveillance tasks.

The friction stems from Anthropic's usage policies that prohibit domestic surveillance applications. The officials, who spoke to Semafor anonymously, said they worry that Anthropic enforces its policies selectively based on politics and uses vague terminology that allows for a broad interpretation of its rules.

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Anthropic's AI models could potentially help spies analyze classified documents, but the company draws the line at domestic surveillance. That restriction is reportedly making the Trump administration angry.

On Tuesday, Semafor reported that Anthropic faces growing hostility from the Trump administration over the AI company's restrictions on law enforcement uses of its Claude models. Two senior White House officials told the outlet that federal contractors working with agencies like the FBI and Secret Service have run into roadblocks when attempting to use Claude for surveillance tasks.

The friction stems from Anthropic's usage policies that prohibit domestic surveillance applications. The officials, who spoke to Semafor anonymously, said they worry that Anthropic enforces its policies selectively based on politics and uses vague terminology that allows for a broad interpretation of its rules.

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Anthropic's AI models could potentially help spies analyze classified documents, but the company draws the line at domestic surveillance. That restriction is reportedly making the Trump administration angry.

On Tuesday, Semafor reported that Anthropic faces growing hostility from the Trump administration over the AI company's restrictions on law enforcement uses of its Claude models. Two senior White House officials told the outlet that federal contractors working with agencies like the FBI and Secret Service have run into roadblocks when attempting to use Claude for surveillance tasks.

The friction stems from Anthropic's usage policies that prohibit domestic surveillance applications. The officials, who spoke to Semafor anonymously, said they worry that Anthropic enforces its policies selectively based on politics and uses vague terminology that allows for a broad interpretation of its rules.

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Health secretary and anti-vaccine activist Robert F. Kennedy Jr. plans to roll back access to lifesaving vaccines for children, and has refused to even speak with staff scientists and subject-matter experts at the Centers for Disease Control and Prevention about evidence-based recommendations. That's according to former CDC officials who testified before the Senate on Wednesday.

The Senate Committee on Health, Education, Labor, and Pensions (HELP) called ex-CDC director Susan Monarez to review the chaos that has engulfed the public health agency under Kennedy. Monarez, a microbiologist and long-serving federal employee, led the CDC as the first Senate-confirmed director for just 29 days before her dramatic ouster last month . She appeared before the HELP committee alongside Debra Houry, the former chief medical officer for the CDC. Houry had worked at the agency for a decade—spanning four administrations and six directors— before resigning in protest against Kennedy's leadership soon after Monarez's ouster.

Monarez’s ouster

Much of their testimony today was alarming, but not surprising. Upon her exit, Monarez claimed that she was fired because she refused Kennedy's demand that she agree in advance to approve changes to the CDC's childhood vaccine recommendations regardless of whether any scientific evidence supported the changes. She also claimed that Kennedy demanded that she fire CDC scientific leadership without cause, which she also refused to do. Similarly, when Houry resigned, she said Kennedy was censoring science, steamrolling CDC experts, and spreading misinformation. In the hearing today, the two stood by their previous comments and provided more details.

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Health secretary and anti-vaccine activist Robert F. Kennedy Jr. plans to roll back access to lifesaving vaccines for children, and has refused to even speak with staff scientists and subject-matter experts at the Centers for Disease Control and Prevention about evidence-based recommendations. That's according to former CDC officials who testified before the Senate on Wednesday.

The Senate Committee on Health, Education, Labor, and Pensions (HELP) called ex-CDC director Susan Monarez to review the chaos that has engulfed the public health agency under Kennedy. Monarez, a microbiologist and long-serving federal employee, led the CDC as the first Senate-confirmed director for just 29 days before her dramatic ouster last month . She appeared before the HELP committee alongside Debra Houry, the former chief medical officer for the CDC. Houry had worked at the agency for a decade—spanning four administrations and six directors— before resigning in protest against Kennedy's leadership soon after Monarez's ouster.

Monarez’s ouster

Much of their testimony today was alarming, but not surprising. Upon her exit, Monarez claimed that she was fired because she refused Kennedy's demand that she agree in advance to approve changes to the CDC's childhood vaccine recommendations regardless of whether any scientific evidence supported the changes. She also claimed that Kennedy demanded that she fire CDC scientific leadership without cause, which she also refused to do. Similarly, when Houry resigned, she said Kennedy was censoring science, steamrolling CDC experts, and spreading misinformation. In the hearing today, the two stood by their previous comments and provided more details.

Read full article

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Health secretary and anti-vaccine activist Robert F. Kennedy Jr. plans to roll back access to lifesaving vaccines for children, and has refused to even speak with staff scientists and subject-matter experts at the Centers for Disease Control and Prevention about evidence-based recommendations. That's according to former CDC officials who testified before the Senate on Wednesday.

The Senate Committee on Health, Education, Labor, and Pensions (HELP) called ex-CDC director Susan Monarez to review the chaos that has engulfed the public health agency under Kennedy. Monarez, a microbiologist and long-serving federal employee, led the CDC as the first Senate-confirmed director for just 29 days before her dramatic ouster last month . She appeared before the HELP committee alongside Debra Houry, the former chief medical officer for the CDC. Houry had worked at the agency for a decade—spanning four administrations and six directors— before resigning in protest against Kennedy's leadership soon after Monarez's ouster.

Monarez’s ouster

Much of their testimony today was alarming, but not surprising. Upon her exit, Monarez claimed that she was fired because she refused Kennedy's demand that she agree in advance to approve changes to the CDC's childhood vaccine recommendations regardless of whether any scientific evidence supported the changes. She also claimed that Kennedy demanded that she fire CDC scientific leadership without cause, which she also refused to do. Similarly, when Houry resigned, she said Kennedy was censoring science, steamrolling CDC experts, and spreading misinformation. In the hearing today, the two stood by their previous comments and provided more details.

Read full article

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