Our STEM All-Star #19 is Rosalind Franklin, Molecular Biologist. Download a printable PDF here.
Rosalind Elsie Franklin (25 July 1920 – 16 April 1958) was a British biophysicist and X-ray crystallographer who made critical contributions to the understanding of the fine molecular structures of DNA, RNA, viruses, coal, and graphite. Franklin is best known for her work on the X-ray diffraction images of DNA which led to discovery of DNA double helix.
Her data, according to Francis Crick, was “the data we actually used” to formulate Crick and Watson’s 1953 hypothesis regarding the structure of DNA. Franklin’s images of X-ray diffraction confirming the helical structure of DNA were shown to Watson without her approval or knowledge. Though this image and her accurate interpretation of the data provided valuable insight into the DNA structure, Franklin’s scientific contributions to the discovery of the double helix are often overlooked. Unpublished drafts of her papers (written just as she was arranging to leave King’s College London) show that she had independently determined the overall B-form of the DNA helix and the location of the phosphate groups on the outside of the structure. Moreover, Franklin personally told Crick and Watson that the backbones had to be on the outside, which was crucial since before this both they and Linus Pauling had independently generated non-illuminating models with the chains inside and the bases pointing outwards. However, her work was published third, in the series of three DNANature articles, led by the paper of Watson and Crick which only hinted at her contribution to their hypothesis.
As 2012 nears its end, one thing stands out as the major theme in human evolution research this year: Our hominid ancestors were more diverse than scientists had ever imagined. Over the past 12 months, researchers have found clues indicating that throughout most of hominids’ seven-million-year history, numerous species with a range of adaptations lived at any given time. Here are my top picks for the most important discoveries this year.
1. Fossil foot reveals Lucy wasn’t alone: Lucy’s species, Australopithecus afarensis, lived roughly 3.0 million to 3.9 million years ago. So when researchers unearthed eight 3.4-million-year-old hominid foot bones in Ethiopia, they expected the fossils to belong to Lucy’s kind. The bones do indicate the creature walked upright on two legs, but the foot had an opposable big toe useful for grasping and climbing. That’s not something you see in A. afarensis feet. The researchers who analyzed the foot say it does resemble that of the 4.4-million-year-old Ardipithecus ramidus, suggesting that some type of Ardipithecus species may have been Lucy’s neighbor. But based on such few bones, it’s too soon to know what to call this species.
2. Multiple species of early Homo lived in Africa: Since the 1970s, anthropologists have debated how many species of Homo lived about two million years ago after the genus appeared in Africa. Some researchers think there were two species: Homo habilis and Homo rudolfensis; others say there was just H. habilis, a species with a lot of physical variation. It’s been a hard question to address because there’s only one well-preserved fossil, a partial skull, of the proposed species H. rudolfensis. In August, researchers working in Kenya announced they had found a lower jaw that fits with the previously found partial skull of H. rudolfensis. The new jaw doesn’t match the jaws of H. habilis, so the team concluded there must have been at least two species of Homo present.
3. New 11,500-year-old species of Homo from China: In March, researchers reported they had found a collection of hominid bones, dating to 11,500 to 14,300 years ago, in a cave in southern China. Based on the age, you’d expect the fossils to belong to Homo sapiens, but the bones have a mix of traits not seen in modern humans or populations of H. sapiens living at that time, such as a broad face and protruding jaw. That means the fossils may represent a newly discovered species of Homo that lived side by side with humans. Another possibility is that the remains came from Denisovans, a mysterious species known only from DNA extracted from the tip of a finger and a tooth. Alternatively, the collection may just reveal that H. sapiens in Asia near the end of the Pleistocene were more varied than scientists had realized.
4. Shoulder indicates A. afarensis climbed trees: Another heavily debated question in human evolution is whether early hominids still climbed trees even though they were built for upright walking on the ground. Fossilized shoulder blades of a 3.3-million-year-old A. afarensis child suggest the answer is yes. Scientists compared the shoulders to those of adult A. afarensis specimens, as well as those of modern humans and apes. The team determined that the A. afarensis shoulder underwent developmental changes during childhood that resemble those of chimps, whose shoulder growth is affected by the act of climbing. The similar growth patterns hint that A. afarensis, at least the youngsters, spent part of their time in trees.
5. Earliest projectile weapons unearthed: Archaeologists made two big discoveries this year related to projectile technology. At the Kathu Pan 1 site in South Africa, archaeologists recovered 500,000-year-old stone points that hominids used to make the earliest known spears. Some 300,000 years later, humans had started making spear-throwers and maybe even bow and arrows. At the South African site called Pinnacle Point, another group of researchers uncovered tiny stone tips dated to 71,000 years ago that were likely used to make such projectile weapons. The geological record indicates early humans made these small tips over thousands of years, suggesting people at this point had the cognitive and linguistic abilities to pass on instructions to make complex tools over hundreds of generations.
6. Oldest evidence of modern culture: The timing and pattern of the emergence of modern human culture is yet another hotly contested area of paleoanthropology. Some researchers think the development of modern behavior was a long, gradual buildup while others see it as progressing in fits and starts. In August, archaeologists contributed new evidence to the debate. At South Africa’s Border Cave, a team unearthed a collection of 44,000-year-old artifacts, including bone awls, beads, digging sticks and hafting resin, that resemble tools used by modern San culture today. The archaeologists say this is the oldest instance of modern culture, that is, the oldest set of tools that match those used by living people.
7. Earliest example of hominid fire: Studying the origins of fire is difficult because it’s often hard to differentiate a natural fire that hominids might have taken advantage of versus a fire that our ancestors actually ignited. Claims for early controlled fires go back almost two million years. In April, researchers announced they had established the most “secure” evidence of hominids starting blazes: one-million-year-old charred bones and plant remains from a cave in South Africa. Because the fire occurred in a cave, hominids are the most likely cause of the inferno, the researchers say.
8. Human-Neanderthal matings dated: It’s not news that Neanderthals and H. sapiens mated with each other, as Neanderthal DNA makes up a small portion of the human genome. But this year scientists estimated when these trysts took place: 47,000 to 65,000 years ago. The timing makes sense; it coincides with the period when humans were thought to have left Africa and spread into Asia and Europe.
9. Australopithecus sediba dined on wood: Food particles stuck on the teeth of a fossil of A. sediba revealed the nearly two-million-year-old hominid ate wood—something not yet found in any other hominid species. A. sediba was found in South Africa in 2010 and is a candidate for ancestor of the genus Homo.
10. Earliest H. sapiens fossils from Southeast Asia: Scientists working in a cave in Laos dug up fossils dating to between 46,000 and 63,000 years ago. Several aspects of the bones, including a widening of the skull behind the eyes, indicate the bones were of H. sapiens. Although other potential modern human fossils in Southeast Asia are older than this find, the researchers claim the remains from Laos are the most conclusive evidence of early humans in the region.
‘Marine’ Fossils May Instead Represent Early Land Dwellers
A controversial new interpretation of several fossils claims that these sac-like organisms may have been some of the earliest land dwellers. Gregory Retallack, of the University of Orgegon, has analysed the rocks these fossils were found in and claims that they formed from terrestrial soil and were not marine. Therefor the organisms that left the fossils must have been terrestrial.
To read the entire article click the image.
South Africa plays a central role in the history of paleoanthropology. Anthropologists and other scientists of the 19th and early 20th century balked at the possibility that Africa was humankind’s homeland—until an ancient hominid was unearthed in South Africa in 1924. Since then, Africa has become the center of human evolution fieldwork, and South Africa has produced a number of iconic hominid fossils and artifacts. Here is a totally subjective list of the country’s most important hominid discoveries.
Taung Child: In 1924, anatomist Raymond Dart pried a tiny fossilized partial skull and brain from a lump of rock. The bones were the remains of a child. The youngster looked like an ape, but Dart also recognized some human qualities. He decided he had found a human ancestor that was so ancient it was still ape-like in many ways. (Later, scientists would determine the bones were nearly three million years old). Dart named the hominid Australopithecus africanus. The Taung Child, known by the name of the place where the fossils came from, was the first australopithecine ever discovered—and the first early hominid found in Africa. After the discovery, anthropologists who were searching for humanity’s origins in Europe and Asia switched their attention to Africa.
Mrs. Ples: Throughout the 1930s and 1940s, paleontologist Robert Broom led the efforts to find hominids in South Africa. He scoured the region’s limestone caves and quarries—the Taung Child came from a quarry—and was well rewarded for his efforts. Of the numerous fossils he uncovered (sometimes with the help of dynamite), his most influential find was a roughly 2.5-million-year-old skull of an adult female hominid now known as Mrs. Ples. Unearthed in 1947 at a site called Sterkfontein, the skull was well preserved and displayed the same mix of ape and human features seen in the Taung Child. Finding an adult version of A. africanus helped convince skeptics that the species was an ancient human ancestor. Some anatomists had thought Taung was just an ape and would have developed more pronounced ape-like features, and lost its human-like traits, as it grew up. Instead, Mrs. Ples showed that the species retained its mix of human and ape traits throughout life.
STS 14: Another one of Broom’s key finds is a set of well-preserved post-cranial bones that includes a pelvis, partial spine, ribs and upper thigh. Like Mrs. Ples, these fossils were found in 1947 at Sterkfontein and date to about 2.5 million years ago. The bones are officially known as STS 14 (STS refers to Sterkfontein) and presumably belonged to an A. africanus individual. The shape of the pelvis and spine are remarkably modern, and the find was some of the first evidence that early human ancestors walked upright on two legs.
SK 48: In addition to finding a trove of A. africanus specimens, Broom, along with his many assistants, discovered a new hominid species: Paranthropus robustus. The first hints of the species came in 1938 when Broom acquired a jaw fragment and molar that were much larger and thicker than any fossils belonging to A. africanus. Broom collected more of the unusual fossils and then hit the jackpot in 1950. A quarry worker found a nearly complete skull of an adult hominid that had giant teeth and a flat face. The fossil is officially called SK 48 (SK refers to the cave of Swartkrans where the skull was found). The collection of fossils with big chompers, which the hominids used to chew tough foods, was given the name P. robustus, which lived in South Africa about 1.8 million to 1.2 million years ago.
Little Foot: In the early 1990s, anthropologist Ron Clarke of South Africa’s University of the Witwatersrand found four small australopithecine foot bones at Sterkfontein. Later, Clarke and his colleagues discovered a nearly complete skeleton embedded in limestone that belonged to the foot. The researchers are still carefully chipping away at the rock to release the skeleton, dubbed Little Foot, but they have already noted that the individual has some characteristics not seen in any other known species of Australopithecus. But since the bones haven’t been fully studied and shared with other scientists, it’s hard to know where the hominid sits in the family tree, Science reported last year. It’s also hard to know exactly how old it is. Clarke’s team places the fossils at 3.3 million years old while other groups using different dating methods say Little Foot is more like 2.2 million years old. Science reported that Little Foot was expected to be fully liberated from its rocky enclosure sometime this year. As far as I know, that hasn’t happened yet.
Australopithecus sediba: The most recent major hominid fossil discovery in South Africa occurred in 2010. Lee Berger of the University of the Witwatersrand led a team that found two partial hominid skeletons at Malapa Cave. Dating to nearly two million years ago, the skeletons indicate that these hominids had their own unique style of walking and spent time both on the ground and in trees. X-ray scans of one of the skulls reveals that some aspects of the brain were more modern than in previous species. Berger and his colleagues therefore think the species, which they named A. sediba, could have given rise to the genus Homo.
Origins of Modern Behavior: Fossils aren’t the only major human evolution discoveries from South Africa. Several coastal cave sites have been treasure troves of artifacts that reveal when and how sophisticated behavior and culture emerged in early populations of Homo sapiens. There have been too many of these discoveries to single any one out. Some of these finds—such as red pigments used 164,000 years ago and shell beads dating to 77,000 years ago—are among the earliest evidence for symbolic thinking in our ancestors. Other artifacts, like 71,000-year-old projectile weapons, indicate early humans could construct complicated, multipart tools that require a lot of planning and foresight to make.
When it’s dark, and we start to fall asleep, most of us think we’re tired because our bodies need rest. Yet circadian rhythms affect our bodies not just on a global scale, but at the level of individual organs, and even genes.
Now, scientists at the Salk Institute have determined the specific genetic switches that sync liver activity to the circadian cycle. Their finding gives further insight into the mechanisms behind health-threatening conditions such as high blood sugar and high cholesterol.
“We know that genes in the liver turn on and off at different times of day and they’re involved in metabolizing substances such as fat and cholesterol,” says Satchidananda Panda, co-corresponding author on the paper and associate professor in Salk’s Regulatory Biology Laboratory. “To understand what turns those genes on or off, we had to find the switches.”
To their surprise, they discovered that among those switches was chromatin, the protein complex that tightly packages DNA in the cell nucleus. While chromatin is well known for the role it plays in controlling genes, it was not previously suspected of being affected by circadian cycles.
Panda and his colleagues, including Joseph R. Eckercircadian cycles, holder of the Salk International Council Chair in Genetics, report their results December 5 in Cell Metabolism.
From Fish to Man: Research Reveals How Fins Became Legs
Dec. 10, 2012 — Vertebrates’ transition to living on land, instead of only in water, represented a major event in the history of life. Now, researchers reporting in the December issue of the Cell Press journal Developmental Cell provide new evidence that the development of hands and feet occurred through the gain of new DNA elements that activate particular genes.
Created using real human tissues, these bone china histology dessert plates are 8” diameter and available in 4 different human tissue designs:
Medical illustrator and artist, Emily Evans, made these gorgeous plates from original slides of various human tissues provided by Michelle Spear, Clinical Anatomist at Cambridge University. The plates were then fired by ceramic artist, Emma Smith.
The discovery of huge amounts of water ice and possible organic compounds on the heat-blasted planet Mercury suggests that the raw materials necessary for life as we know it may be common throughout the solar system, researchers say.
Image: The radar image of Mercury’s north polar region from Image 2.1 is shown superposed on a mosaic of MESSENGER images of the same area. All of the larger polar deposits are located on the floors or walls of impact craters. Deposits farther from the pole are seen to be concentrated on the north-facing sides of craters. Image released Nov. 28, 2012. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington/National Astronomy and Ionosphere Center, Arecibo Observatory
Mercury likely harbors between 100 billion and 1 trillion metric tons of water ice in permanently shadowed areas near its poles, scientists analyzing data from NASA’s Messenger spacecraft announced Thursday (Nov. 29).
Life on sun-scorched Mercury remains an extreme longshot, the researchers stressed, but the new results should still put a spring in the step of astrobiologists around the world.
“The more we examine the solar system, the more we realize it’s a soggy place,” Jim Green, the director of NASA’s Planetary Science Division, said during a press conference today.
“And that’s really quite exciting, because that means the amount of water that we have here on Earth — that was not only inherent when it was originally formed but probably brought here — that water and other volatiles were brought to many other places in the solar system,” Green added. “So it really bodes well for us to continue on the exploration, following the water and its signs throughout the solar system.”
The Fibonacci Series is a sequence of numbers first created by Leonardo Fibonacci (fi-bo-na-chee) in 1202. It is a deceptively simple series, but its ramifications and applications are nearly limitless. It has fascinated and perplexed mathematicians for over 700 years, and nearly everyone who has worked with it has added a new piece to the Fibonacci puzzle, a new tidbit of information about the series and how it works. Fibonacci mathematics is a constantly expanding branch of number theory, with more and more people being drawn into the complex subtleties of Fibonacci’s legacy.
Much of the internet is buzzing over upcoming “big news” from NASA’s Curiosity rover, but the space agency’s scientists are keeping quiet about the details.
The report comes by way of the rover’s principal investigator, geologist John Grotzinger of Caltech, who said that Curiosity has uncovered exciting new results from a sample of Martian soil recently scooped up and placed in the Sample Analysis at Mars (SAM) instrument.
“This data is gonna be one for the history books. It’s looking really good,” Grotzinger told NPR in an segment published Nov. 20. Curiosity’s SAM instrument contains a vast array of tools that can vaporize soil and rocks to analyze them and measure the abundances of certain light elements such as carbon, oxygen, and nitrogen – chemicals typically associated with life.
The mystery will be revealed shortly, though. Grotzinger told Wired through e-mail that NASA would hold a press conference about the results during the 2012 American Geophysical Union meeting in San Francisco from Dec. 3 to 7. Because it’s so potentially earth-shaking, Grotzinger said the team remains cautious and is checking and double-checking their results. But while NASA is refusing to discuss the findings with anyone outside the team, especially reporters, other scientists are free to speculate.
“If it’s going in the history books, organic material is what I expect,” says planetary scientist Peter Smith from the University of Arizona’s Lunar and Planetary Laboratory. Smith is formerly the principal investigator on a previous Mars mission, the Phoenix lander, which touched down at the Martian North Pole in 2008. “It may be just a hint, but even a hint would be exciting.”
Smith added that he is not in contact with anyone from the Curiosity team about their results and offered his assessment as an informed outside researcher.
Organic molecules are those that contain carbon and are potential indicators of life. During its mission, Phoenix heated a sample of soil to search for organics but these efforts were stymied by the presence of perchlorates, chemical salts that sit in the Martian soil. Perchlorates react to heat and destroy any complex organic molecules, leaving only carbon dioxide, which is abundant in the Martian atmosphere.
The Viking landers, which explored opposite sides of Mars in the late 1970s, also conducted a search for organic molecules and came up empty. For decades afterward, astronomers considered Mars to be a dead planet, with conditions not very conducive to life. After the results from Phoenix, scientists realized that perchlorates were probably messing with those earlier findings as well, and could account for their negative outcome.
Curiosity’s suite of laboratory instruments are able to slowly heat a sample in a way that doesn’t trigger the perchlorates. They can also weigh any molecules present, determining how much carbon, oxygen, and hydrogen they are made from. Simple organic compounds wouldn’t be completely shocking, said Smith, since these probably come from meteorites originating in the asteroid belt and probably are around on present-day Mars. But they would indicate that the building blocks for life are present on Mars and might only need the addition of water, which Mars had in the past, in order to produce organisms.
“If they found signatures of a very complex organic type, that would be astounding,” said Smith, since they would likely be leftovers from complex life forms that once roamed Mars. But the odds of finding such a startling result in a sample of sand scooped from a random dune are “very, very low,” Smith said.
Smith cautioned against speculating too much, since rumors have a way of spreading rapidly when it comes to any discussion of potential life on Mars. During his tenure on the Phoenix mission, his team was evaluating the interesting perchlorate results, which they kept secret during analysis. Rumors got out and then became worse when some unsubstantiated report claimed a member of his team meeting was meeting with the White House.
“When you keep things secret, people start thinking all kinds of crazy things,” he said.
‘Bio-Bots’ Can Walk on Their Own
They’re soft, biocompatible, about 7 millimeters long – and, incredibly, able to walk by themselves. Miniature “bio-bots” developed at the Univ. of Illinois are making tracks in synthetic biology.
Designing non-electronic biological machines has been a riddle that scientists at the interface of biology and engineering have struggled to solve. The walking bio-bots demonstrate the Illinois team’s ability to forward-engineer functional machines using only hydrogel, heart cells and a 3D printer.
Read more: http://www.laboratoryequipment.com/news/2012/11/%E2%80%98bio-bots%E2%80%99-can-walk-their-own
Lucy and Ardi are the poster children of human evolution. But these famous fossil skeletons may never have been found if it weren’t for Louis and Mary Leakey’s pioneering efforts. The pair made several discoveries at Tanzania’s Olduvai Gorge in the 1950s and 1960s that inspired other anthropologists to come to East Africa in search of human ancestors. Here’s a look at some of the most important hominid fossil finds from Tanzania.
The Nutcracker Man (OH 5): The Leakeys’ first major discovery at Olduvai Gorge occurred in 1959. Mary found the roughly 1.8-million-year-old skull of a hominid with a flat face, gigantic teeth, a large crest on the top of its head (where chewing muscles attached) and a relatively small brain. They named the species Zinjanthropus boisei (now known as Paranthropus boisei). Nicknamed the Nutcracker Man, the species was too different from modern people to be the direct human ancestor that Louis had been hoping to find. But the discovery captured public interest in human evolution, and the Leakeys went on to unearth many more hominid fossils at Olduvai. OH 5 is the fossil’s official catalog name, meaning Olduvai Hominid Number 5.
Johnny’s Child (OH 7): The next big Leaky discovery came in 1960. Mary and Louis’ son, Johnny, found a lower jaw about 300 yards away from where the Nutcracker Man was discovered. The bone came from a young hominid; thus, the fossil was nicknamed Johnny’s Child. At the same spot, the Leakeys also dug up some hand bones and skull fragments. Using these skull fragments, the Leakeys and their colleagues estimated the roughly 1.8-million-year-old hominid’s brain size: 680 cubic centimeters. That was significantly bigger than the size of the average australopithecine brain, about 500 cubic centimeters. The hand bones revealed that the hominid had a “precision grip,” when a fingertip presses against the tip of the thumb. This movement allows for fine manipulation of objects, such as turning a key in a door or threading a needle. The precision grip led the Leakeys to conclude that this hominid was the one who made the stone tools found at Olduvai. Because of the tool-making and the big brain, the Leakeys decided OH 7 represented the earliest member of the genus Homo: Homo habilis (meaning Handy Man).
OH 8: Also in 1960, the Leakeys’ team discovered a well-preserved fossil foot belonging to H. habilis. The bones indicate the hominid had modern-looking foot arches, suggesting the species walked like modern people do. Tooth marks on the specimen’s ankle reveal the hominid had been a crocodile’s lunch.
OH 9: At the same time the Leakeys unearthed the first examples of H. habilis, they also recovered the skull cap of a more recent hominid dating to about 1.4 million years ago. At 1,000 cubic centimeters, the specimen’s brain was much bigger than that of H. habilis. The skull had thick brow ridges and a low, sloped forehead—key features linking the fossil to the species Homo erectus.
Twiggy (OH 24): Discovered in 1968 by Peter Nzube, Twiggy is a skull belonging to an adult H. habilis dating to roughly 1.8 million years ago. Although OH 24 is the most complete H. habilis skull from Olduvai Gorge, it was found crushed completely flat (and therefore named after the slender British model of the same name). Paleoanthropologist Ron Clarke reconstructed what the skull would have looked like, but it’s still fairly distorted.
LH 4: In the 1970s, after Louis died, Mary began excavations at Laetoli, about 30 miles from Olduvai Gorge. The fossils she was finding there were much older than the bones she and Louis had discovered at Olduvai. In 1974, for example, her team unearthed a lower jaw with teeth dating to 3.6 million years ago. It was cataloged as Laetoli Homind 4, or LH 4. Around the same time, anthropologists at the site of Hadar in Ethiopia were also finding hominid fossils dating to more than 3 million years ago, including the famous Lucy skeleton. At first, no one was sure what to call these older fossils. After analyzing both the Hadar and Laetoli specimens, anthropologists Tim White and Donald Johanson (Lucy’s discoverer) concluded that all of the fossils represented one species that they called Australopithecus afarensis. They chose LH 4 as the species’ type specimen, or the standard representative of the species. Mary did not approve. She didn’t believe the fossils from Laetoli were australopithecines. But under the rules of taxonomy, once a type specimen is designated, it’s forever associated with its species name. (For more on the controversy, see Johanson’s book Lucy.)
Laetoli Footprints: In 1978, one of Mary’s team members, Paul Abell, made the most famous discovery at Laetoli: He found the trail of about 70 fossilized hominid footprints. Based on the footprints’ age, 3.6 million years, anthropologists think they were made by an A. afarensis group. The footprints reveal this early hominid had a very modern way of walking. The big toe was in line with the other toes, not off to the side like an ape’s big toe. And the prints reveal the walkers had arches, unlike the flat feet of an ape. The footprints also suggest A. afarensis had a modern gait.
Around 500 years ago, Leonardo da Vinci briefly focused his attention on fossils — and inadvertently triggered a mystery that remains unsolved.
A page of Leonardo’s Paris Manuscript I is covered in sketches of marine fossils; among them is a honeycomb-like array of hexagons that palaeontologists think might constitute the first recorded observation of an enigmatic trace fossil called Paleodictyon1. The fossil is thought by many paleontologists to be an imprint of burrows made by an animal living in loose sediment on the sea floor. Examples of Paleodictyon have been found that date back to the Cambrian period, 542 million to 488 million years ago, and similar structures are still being made on the sea floor today.
But the identity of the animal that generates the hexagons remains elusive. A set of similar, but simpler, fossils could explain why — and one researcher says that they could show that organisms started caring for their young millions of years earlier than thought.
Resolving the riddle of our earliest vertebrate ancestors
The questions of how, when and why our earliest fish-like ancestors evolved are fundamental to understanding our place in evolution. However, answers remain elusive because we don’t know how to read the earliest vertebrate fossil record.
Progressive stages of decay of a close relative of vertebrates, the lancelet (AKA amphioxus). As they rot, specimens look more and more like fossils from the earliest parts of the vertebrate evolutionary tree. (Purnell, Sansom, Gabbott, University of Leicester). (royalsociety.org)