A row has broken out over two ‘alien corpses’ that were presented in Mexico this week, with an American UFO specialist criticizing the ‘unsubstantiated stunt’.

The corpses were unveiled to a stunned Mexican congress by journalist and UFO enthusiast Jaime Maussan and forensic scientist Dr Jose Zalce Benitez.

But the presentation sparked a swift backlash with Navy Lt Ryan Graves, who has participated in US Congressional hearings about Unidentified Anomalous Phenomena (UAP), calling it a ‘huge step backwards’.

In a follow-up press conference today, Mr Maussan said he was disappointed by the comments, while Dr Benitez challenged scientists to take samples of the alleged alien bodies and conduct their own studies.

He also warned sceptics calling the ‘discovery’ a hoax to be mindful that their claims could destroy his life’s work.

The two ‘alien corpses’ were unveiled to a stunned Mexican congress this week

Navy Lt. Ryan Graves, who has taken part in US Congressional hearings about Unidentified Anomalous Phenomena (UAP), called the presentation a ‘huge step backwards’

Graves wrote after the hearing that he was ‘disappointed by this unsubstantiated stunt’

Mexican journalist and UFO expert Jaime Maussan observes the ‘non-human’ beings before a press conference 

Mr Maussan testified under oath before Mexican lawmakers that ‘we are not alone’ in the universe and displayed the alleged remains of non-human beings.

In the hearing on Tuesday on FANI, politicians were shown two artefacts by the journalist, who claimed they were the corpses of extraterrestrials.

The specimens were not related to any life on Earth, Mr Maussan said. 

The two tiny ‘bodies,’ displayed in cases, have three fingers on each hand and elongated heads. Mr Maussan said they were recovered in Peru near the ancient Nazca Lines in 2017. He said that they were about 1,000 years old, analyzed through a carbon dating process by Mexico’s National Autonomous University (UNAM). 

But sceptics questioned the authenticity of his presentation, with Lt Graves writing on X: ‘After the U.S. Congressional UFO hearing, I accepted an invitation to testify before the Mexican Congress hoping to keep up the momentum of government interest in pilot experiences with UAP.

‘Unfortunately, yesterday’s demonstration was a huge step backwards for this issue. My testimony centered on sharing my experience and the UAP reports I hear from commercial and military aircrew through ASA’s witness program. 

‘I will continue to raise awareness of UAP as an urgent matter of aerospace safety, national security, and science, but I am deeply disappointed by this unsubstantiated stunt.’

The bodies shown at congress were roughly humanoid in shape. But a retractable neck and long skull show characteristics more ‘typical of birds’, El País reported  

The body, presented in a glass box, was seen with three fingers on its hand

They were also found to have strong, light bones and no teeth, the presenters said 

Mr Maussan said that while similar such finds in the past have turned out to be the remains of mummified children, this was the first time such evidence had been presented.

He added: ‘I think there is a clear demonstration that we are dealing with non-human specimens that are not related to any other species in our world and that all possibilities are open for any scientific institution… to investigate it. We are not alone.’

Dr Benitez said X-rays, 3-D reconstruction and DNA analysis had been carried out on the remains and added: ‘I can affirm that these bodies have no relation to human beings.’

The bodies shown at congress were roughly humanoid in shape. But a retractable neck and long skull show characteristics more ‘typical of birds’, El País reported.

They were also found to have strong, light bones and no teeth, the presenters said.

Experts in congress showed apparent X-rays of the specimens and said that one of the beings carried ‘eggs’ with embryos inside them.

They said they had implants of cadmium and osmium metals. 

Osmium is one of the most scarce elements in the Earth’s crust and considered the rarest precious metal.

Researchers are said to have carbon dated the remains and found they were more than 1,000 years old

Researchers made the extraordinary claim that the corpses, recovered from Peru had a genetic composition 30 per cent removed from that of human beings

Photo shows an annotated close-up of the body during Tuesday’s presentation in Mexico

UNAM on Thursday republished a statement first issued in 2017, saying the work by its National Laboratory of Mass Spectrometry with Accelerators (LEMA) was only intended to determine the age of the samples. 

‘In no case do we make conclusions about the origin of said samples,’ it said.

Mexican lawmakers also heard from Lt Graves, who gave testimony earlier this year on ‘UAP’ sightings and government classification. He made claims in July about the threat UAPs pose to America’s national security. 

Lt Graves claimed UFOs were an ‘open secret’ in the military and testified his squadron regularly detected unidentified objects while stationed near Virginia in 2014.

Congressman Sergio Gutierrez said he hoped the hearing would be the first of other similar events in Mexico.

‘We are left with reflections, with concerns and with the path to continue talking about this,’ Mr Gutierrez said.

In recent years, the US government has done a U-turn on public information on UAP after decades of stonewalling and deflecting. 

The Pentagon has been actively investigating reported sightings in recent years by military aviators, while an independent Nasa panel studying UFOs is the first of its kind by the space agency.

Journalist and UFO researcher Jaime Maussan speaks during a briefing on unidentified flying objects, known as UFOs, in Mexico City

The row comes as Nasa prepares to release the findings of a long-awaited study on unexplained flying objects in Earth’s skies.

The US space agency announced last year that it was reviewing evidence regarding UAPs – which has replaced the term ‘UFO’ in official parlance.

The subject has long fascinated the public but was shunned by mainstream science.

An independent team of 16 researchers shared their preliminary observations in May, finding that existing data and eyewitness reports are insufficient to draw firm conclusions, while calling for more systematic collection of high-quality data.

It’s unlikely Thursday’s report will change that bottom line – but it could eventually usher in the start of a new mission for the agency.

While Nasa’s probes and rovers scour the solar system for any fossils of ancient microbes, and its astronomers look for signs of intelligent civilisations on distant planets, its historic posture has been to ‘debunk’ sightings on our home planet.

There have been more than 800 ‘events’ collected over 27 years, of which 2 to 5 per cent are thought to be possibly anomalous, the report’s authors said during the May meeting.

These are defined as ‘anything that is not readily understandable by the operator or the sensor,’ or ‘something that is doing something weird,’ said team member Nadia Drake.

Experts including congressman Sergio Gutierrez, Lt Ryan Graves and Jaime Maussan attend a briefing on unidentified flying objects

The US government has begun taking the issue of UAPs more seriously in recent years, in part due to concerns that they are related to foreign surveillance.

Nasa’s work, which relies on unclassified material, is separate from a Pentagon investigation, though the two are coordinating on matters of how to apply scientific tools and methods.

In July, a former US intelligence officer made headlines when he told a congressional committee he ‘absolutely’ believes the government is in possession of unidentified anomalous phenomena – as well as remains of their alien operators.

‘My testimony is based on information I’ve been given by individuals with a longstanding track record of legitimacy and service to this country – many of whom also shared compelling evidence in the form of photography, official documentation and classified oral testimony,’ David Grusch told lawmakers.