|Posted by Kevin on May 27, 2015 at 10:50 PM||comments (0)|
Jun 23, 2014
I met a long lost cousin yesterday.
Or rather, a long line of them. In fact, an incredibly long line of cousins stretching back a billion years or so.
One of them was from the Comb Jellies era, which you may associate with greasy Brylcreem products from the 1950s and the line "Kookie, Kookie, Lend me Your Comb."
Am I dating myself yet?
If so, that's actually a good thing, because "Comb Jellies" are life forms properly titled Ctenophara that live in marine waters all over the world. They have combs used for swimming, making them the largest animals that swim using cilia, tiny comblike projections.
Ctenophara date from about 730 million or so years ago. They're one of many of our ancestors who are still hanging around (or should it be hanging on?) on earth.
Just after 8 a.m. Sunday, a group of some 50 people gathered at Erindale Park to take part in the fourth annual Ancestor's Trek, the evolutionary annual hike organized by Mississauga veterinarian Dr. Kevin Saldanha who is a mainstay of the Halton-Peel Humanist Community.
He's borrowed the thematic bent of a book called The Ancestor's Tale and translated it into a local annual trek that combines several agreeable elements including walking, heritage, science and education.
For background on the concept, check out Joseph Chin's excellent advance story for this year's event:
While lifeforms have been around for 3.5 billion of earth's 4.5 billion years, the party didn't actually start with Paris Hilton.
It started when cells decided to get together and then divide, one of those far-sighted early breakup and recombination reality concepts that always get such good ratings.
"We do have a kinship with many other things and we will be following the path that humans took," explained the long-time Mississauga resident as the event kicked off in bright sunshine. "Each stride you take represents about 60,000 years.
"The time that humans have been on earth in the form we have today" (~200,000y) would be taken up in the last 3 strides that each walker took yesterday at the end of the hike in Pinecliff Park, he explained.
Talk about readjusting your scale of measurement. If that fact alone doesn't do it, how about all recorded history (about 5000 years) would fit into 6 cm (a palm width) or our entire modern world (constructed during the last 300 years since the industrial revolution) would be about 1.5cm of that (a mere thumbs width).
The walk stretched 12.5 km from Erindale Park along the Culham Trail that winds beside the Credit River, all the way up to Pinecliff Park in Meadowvale South, just south of Kenninghall Blvd.
At various information signposts along the way, Saldanha reintroduced us to our cousins the Choanoflagellates (there's one who overdoes it in every family), the sponges, the placozoans (literally "flat animals") and eventually to the jellyfish, dinosaurs and the monkeys. In other words, the regulars who always show up at the annual reunion.
Periodically, Saldanha would wax philosophic on the potential end of the story, noting for instance that the last of the five "extinction" events in earth's history killed the dinosaurs and wiped out all the other mammals on earth, with the exception of one burrowing mole species, from which we (and all other mammals from mice to whales) are all descended. And we are now contributing to the 6th great extinction judging from the number of species going extinct due to pollution, deforestation and climate change.
Another of our common ancestors, coral which counteracts ocean acidification and provides critical habitat for fish to spawn, is in major, major difficulty due to ocean warming and elevated carbon dioxide levels, he explained.
Commercial fishing for shrimp and prawns is doing major damage to coral reefs.
"It's like losing the rainforest of the sea," Saldanha said. "This is not just about our common ancestry. It also teaches us a little bit about how we, as humans, are changing the environment.
"That's not to say that everyone has to go vegan," he added. "But just be a little bit more aware of what we're doing when you go to Red Lobster."
At that point, standing underneath the Highway 403 bridge Saldanha reminded walkers that they could still get their Ancestor's Trail "passports" marked for various prehistoric checkpoints.
"Don't worry if you don't get them marked, you'll still get a hot dog at the end," he added.
"With no shrimp," some wit pointed out.
The presence of former Ward 6 Councillor David Culham, for whom the trail was named, made it a historical, environmental and political education as well as a scientific one.
He recalled the days when much of Erindale Park was actually Erindale Lake, part of a hydro-electric plant whose remnants can still be seen in some areas. It's unlikely many of its users also know the park, like so many others including Port Credit Memorial, was originally a garbage dump.
As the trail wended its way through Hewick Meadows, Culham recalled the late night call he received many years ago from local planning consultant John Rogers which triggered his even more late-night negotiations with Steve Hewick, which resulted in a negotiated deal in which the land below the top of bank was donated to the city.
Culham thinks the clincher to the deal was his appeal to Hewick that other children should be able to learn to kayak on the stretch of river the same way that his children did.
The former Ontario Municipal Board member was also able to fill in the historical reason for the gap in the trail in Streetsville. While ADM Milling on Barbertown Rd. has granted an easement through its lands, hard feelings between Kraft Milling and the residents — hard feelings that ended with a messy Ontario Municipal Board hearing — still haven't healed.
But Culham remains optimistic about eventually getting access along the valley right through Streetsville and north of Highway 401 in Meadowvale Village where negotiations have been going on for years.
As participants reached the end of Ancestor's Trail, they got an up close and personal chance to communicate with their reptile relatives, including an albino Burmese python, Argentinian black and white tegu and frilled dragon iguana, which were brought to the site by local reptile enthusiasts.
And, as promised, there were hot dogs.
With nary a shrimp in site.
Photos by John Stewart
Dr. Kevin Saldanha (right) is thanked for organizing the annual Ancestor's Trail hike by Ward 6 Councillor Ron Starr. Photo by John Stewart
An angler tries in luck in the middle of the Credit.
The crowd included about 50, not counting pets.
The event travels the Culham trail, on the east side of the Credit River.
Markers along the way detailed the life forms that preceded human beings.
Dr. Kevin Saldanha started Ancestor's Trail four years ago and continues to lead the way. Here he explains the importance of sponges at a stop below Highway 403.
A stop at Hewick's Meadow, just south of Eglinton Ave. W.
This stop behind River Grove Community Centre, detailed one of five extinction events in the earth's history.
There's always time to stop and take a photo of the scenic Credit.
A commemorative photo at Pinecliffe Park marks the end of Ancestor's trail, for this year.
A frilled dragon iguana, on display t the end of the hike, enjoyed a sunbath on his owner's shoulder.
An Argentinian black and white tegu spoke with forked tongue, and got lots of attention.
An albino Burmese python was willing to pose for photos with some walkers to provide a memento of the 12.5 km. trek
Photos by John Stewart
This Argentinian black and white tegu was a big hit at the end of the Ancestors' Trail 12.5 km. walk along the Credit River Valley Sunday. The trail included a series of stops that highlighted the forerunners of humans, including reptiles. Photo by John Stewart.
|Posted by Kevin on June 19, 2014 at 10:10 PM||comments (0)|
Hike offers a pilgrimage to the dawn of life
Staff photo by Rob Beintema
Mississauga veterinarian Kevin Saldanha will lead an Ancestor’s Trail hike, tracing one billion years of evolution, along the Culham Trail on Sunday. The walk is based on The Ancestor’s Tale by famed British evolutionist Richard Dawkins. From left, Saldanha,volunteer Teresa Tang, and his wife, Lisette, with pooch Pingu.
By Joseph Chin
MISSISSAUGA — Ten years ago, famed evolutionist Richard Dawkins published The Ancestor’s Tale, a book loosely modelled on Chaucer’s Canterbury Tales.
Instead of pilgrims journeying to Canterbury, Dawkins’ protagonists are living species — humans included — travelling back through evolutionary time to their point of origin.
The book, which was nominated for the 2005 Aventis Prize for Science Books, inspired a series of Ancestor’s Trail hikes in the author’s native England.
But you don’t have to flit across the pond to participate in one. Here in Mississauga, it’s replicated by Kevin Saldanha, who, when he read The Ancestor’s Tale, got the idea to recreate that march through time along the Culham Trail.
This year’s hike — the fourth such — takes place Sunday from 8 a.m. to 12:30 p.m.
Although the hike, as described in the book, was originally conceived as a walk back in time, Saldanha decided (for logistical reasons) to plot the hike starting with the dawn of multicellular life approximately one billion years ago and ending with modern man.
The 12.5-kilometre trek starts from Erindale Park and, roughly following the banks of the Credit River, ends with a barbecue lunch at Pinecliff Dr. Park in Streetsville. For a less taxing outing, participants can also join the hike at various points along the route. Go to http://www.ancestorstrail.ca/ for rendezvous times and pledge instructions.
Saldanha has set up the trail so each stride of 0.75 metres represents 60,000 years. A scant 6.25 centimetres represents 5,000 years of human civilization.
“The purpose of this hike is to inform participants of the breathtaking length of geological time necessary for evolution to take place,” he said. “The trail changes your world view. It changes the way you look at other life forms when you identify with our evolutionary cousins.”
At a gingerly pace of approximately three to four kilometres per hour the hike will take about three to four hours. There will be rest and refreshments stops and checkpoints where participants can get their passports stamped while discussing specific issues on evolution and species in distress.
Saldanha says the notion of a common ancestry, that humans came from other beings and not just apes, isn’t something taught in most schools.
“You know it at the back of your mind but it doesn’t hit you until you realize that a fish is your cousin, a coral is your cousin,” he said. “You’ve got the same DNA in your cells that those organisms have in their cells. The genetics, the DNA sequencing, proves that we have common DNA and genes.”
The biggest challenge during the hikes, says Saldanha — who, when he’s not pondering evolution, works as a veterinarian — is helping participants comprehend the scale of time.
“The concept of geological time is so difficult to grasp, not just for kids but for adults,” he said. “That’s why the reluctance to believe in evolution. If you don’t understand geologic time, then it’s really difficult to understand evolution.”
Saldanha says science offers the best explanation for the way in which humans fit into the world. “We’re destroying that web of life that we’re intricately connected to. As those connections are breaking down, we’re putting humanity at risk.”
|Posted by Kevin on June 21, 2013 at 12:05 AM||comments (0)|
Take a hike on the evolutionary trail
Ancestor's Trail Supplied photo
The 2012 Ancestor's Trail proved popular and educational for those who took part.
MISSISSAUGA — If you have the grit to look your evolutionary past straight in the eye, you might want to try the Ancestor Trail this Sunday at Erindale Park.
The walk goes from 8 a.m.-1 p.m. and follows 12.5 kilometres of the Culham Trail.
Starting at Erindale Park, hikers will register and proceed on a pilgrimage to view our common ancestors, or concestors, over the past billion years. That means looking past cute primates with soulful eyes to creatures like bony fish and, a billion years further back still, multi-cell organisms.
Designed by veterinarian Kevin Saldanha, the trail is set up so each human stride of 0.75 metres represents 60,000 years. A scant 6.25 centimetres represents 5,000 years of human civilization.
The timeline is geological and the trail represents one billion years of evolutionary development. That takes the hiker back to multi-cell life forms on Earth. Not exactly creatures we identify with and certainly not cute or cuddly.
"We treat animals differently based on their usefulness to us," said Saldanha.
That doesn't mean we treat useful animals well. He cites the way cattle are de-horned and have their tails docked without anesthetic.
At each milestone, hikers can read about the creature that is the concestor to all life on Earth.
Turns out our ancestors aren't necessarily creatures that would frequent Creditview Animal and Bird Hospital, where Saldanha practices.
It makes sense that humans have non-human and non-primate, and even non-mammal ancestors, but it's not something we usually consider.
“You know it at the back of your mind, but it doesn’t hit you until you realize that a fish is your cousin, a coral is your cousin,” said Saldanha. “You’ve got the same DNA in your cells that those organisms have in their cells. The genetics, the DNA sequencing, proves that we have common DNA and genes.”
Keeping the scale constant means not a lot happens until 500 million years. That's when the hag fish shows up — probably not the kind of ancestor anyone brags about. It's an eel-shaped marine animal that produces slime — and the only living animal that has a skull, but no spine.
Saldanha says once you recognize a fish as an ancestor, it's hard to feel comfortable about sport fishing.
It's not until 300 million years ago that amphibians and reptiles show up — animals that continue to exist.
"The trail changes your world view," said Saldanha. "It changes the way you look at other life forms when you identify with our evolutionary cousins."
The experience highlights the importance of preserving biodiversity — a diversity of life forms that he says is being destroyed by humans changing the environment.
This year Saldanha is requesting hikers donate or take pledges to offset the cost of organizing the Ancestor Trail.
It's not necessary to walk the whole distance. On his website (www.ancestorstrail.ca), there's a full outline of the trail that shows when and where people can join the hike.
In advance of the walk, there will be a presentation at the Mississauga Central Library about the Ancestor Trail and the book that inspired it, The Ancestor's Tale, by Richard Dawkins, on Saturday at 2 p.m.
|Posted by Kevin on June 5, 2013 at 1:20 PM||comments (0)|
May 30, 2013 | Author:Freelance Writer Margo Pierce
Kevin Saldhana (center) takes people on a 12.5-kilometer hike back to the beginning of multi-cellular life on Earth to help them understand our connection to other living beings. (Photo: Courtesy of the Ancetor's Trail Hike)
If a single human stride (0.75 meters/.82 yards) is equivalent to 60,000 years, then 6.25 centimeters (2.46 inches) represents the duration of human civilization, which is only 5,000 years old. That means a 12.5-kilometer (7.7-mile) hike would cover approximately one billion years of evolutionary time, back to the beginning of multi-cellular life on Earth. But who would make such a calculation and why? Kevin Saldhana did. He’s a veterinarian in Ontario, Canada, and the founder of the Ancestor’s Trail Hike in Mississauga, Ontario.
The hike is an opportunity to combine education about the natural world. A pre-set route is mapped against a specific timeline in Earth’s history. During the hike there are stops, called milestones, where hikers learn about different developments in the lifecycles of creatures on the planet. The goal is to go back in time to learn about human ancestors that didn’t look like people but are still part of our biological family.
This in turn creates an opportunity for humans to understand the importance of preserving biodiversity. For Saldhana, one of the many volunteers who will participate in the third annual hike June 23, the link between humans and all living beings is essential to reverse the devastation of the natural world by human exploitation.
Having studied evolution during his schooling, Saldhana thought he had a good sense of the connection between humans and other living beings. But the notion of a common ancestry, that humans came from other beings and not just apes, isn’t something taught in most schools.
“You know it at the back of your mind but it doesn’t hit you until you realize that a fish is your cousin, a coral is your cousin,” he says. “You’ve got the same DNA in your cells that those organisms have in their cells. The genetics, the DNA sequencing, proves that we have common DNA and genes.”
The Ancestor's Tale: A Pilgrimage to the Dawn of Evolution by Richard Dawkins takes readers from modern day back through time to identify common ancestors. The book gave Saldhana the idea to recreate that virtual march through time along the Culham Trail, which follows the Credit River in the western portion of Mississauga. The biggest challenge was helping participants comprehend the scale of time.
“The concept of geological time is so difficult to grasp, not just for kids but for adults,” Saldhana says. “That’s why the reluctance to believe in evolution. If you don’t understand geologic time, then it’s really difficult to understand evolution. This would be an ideal opportunity to show people that on a hike.”
The start of the hike begins in the past. Each step moves people closer to present day.
“I’ve only plotted the last billion years from the time multi-cellular life started,” Saldhana says. “I decided to keep the scale constant, so for the first several hundred million years there’s not much happening until you get to about 500 million years ago, where the hag fish (appear), and the shark and boney fish about 450 million years ago. As you get down to 300 million, where the amphibians and reptiles (appear), it starts getting exciting. You can actually relate to animals that you see today.”
As life begins to appear, the hikers stop at “rendezvous” points to learn about the animals from non-governmental organizations (NGOs), naturalists and other experts. On the 2011 hike, the 6 million year rendezvous focused on the primates of that time. Abner Lico of the Jane Goodall Institute's Roots & Shoots program also talked about the youth leadership program related to environmental issues.
Part of the Ancestor’s Trail Hike is a fundraiser for Roots & Shoots. The youth environmental organization connects kids of all ages around the world who “share a desire to create a better world,” by identifying problems in their communities and taking action through service projects and an interactive website. This was added as the result of feedback from hikers who wanted to give something back.
Saldhana believes that kind of direct action will come from recognizing that human beings have a responsibility to care for the world from which we come. The science of the past and present creates the understanding of why the fate of other beings should matter to us.
“About 440 million years ago we had a common ancestor with boney fish, which is somewhere between lung fish and sharks,” he says. “A lot of people may understand a common ancestry with chimps, bonobos and maybe even apes, but when you talk about fish they say, ‘Fish are so different from us. How could we have a common ancestor with them?’”
Saldhana explains by using the anatomy of modern day humans to draw a connection -- the vertebra in our spinal column formed in the early boney fish. And the gills of a fish evolved over time into a structure used for hearing sound, our ears.
“I usually tell people I’m not making up this stuff because it’s probably the first time they’ve heard it. They can go back and they can read up on it and see how, even through embryology, when a human embryo is conceived, the whole structure looks very much like a tadpole, which looks similar to other mammals at that stage.”
Hiker and 2011 trail volunteer Vishal Murthy points out that hikers can get more information on the spot. QR codes on signs at the various stops on the route allow a smartphone to access additional resources about the animals and time period represented. A student of veterinary medicine, Murthy was working with Saldanha when the first hike was organized.
“I felt that this walk really drove home the scope and enormity of time and the process of change on our planet,” Murthy says. “Learning about evolution is one thing, but to actually walk the trail as we went from one ancestor to another, it really helped put into perspective how much history we share with animals and how short a time we as humans have truly spent on the Earth."
One of the ancient life forms still alive today is coral and it serves to illustrate the impact humans are having on the existence of others to whom we’re connected. The acidification of ocean water causes coral bleaching, which in turn destroys the incubator of the marine food chain, according to Saldanha. He invites groups working to reverse this kind of destruction to present information to hikers at the milestones. (See the milestones on the Google trail map)
United Conservationists is one of the groups that volunteered to help with the Ancestor’s Trail hike. They included the movie Shark Water by, Toronto filmmaker Rob Stewart, as part of the information they shared. It serves as an illustration of what Saldhana wants people to learn from evolution, geologic time and humanity.
The fins are harvest by cutting all of them from the bodies of live sharks. Then the body is thrown back into the ocean.
“They can’t swim, so they sink to the bottom of the ocean and die,” Saldhana explains. “There are things that we’re doing that are unsustainable, are really cruel.
Raising this kind of awareness is considered political by some, even though Saldhana says his focus is on science. He believes fact, not religious beliefs or political agendas, is what’s needed for people to learn the truth about the state of the natural world. But difficulties still arise. One of the largest hiking clubs in the area refused to promote the Ancestor’s Trail hike to its membership, stating, “People will see it as a threat to their religion, so we won’t promote it.”
Saldhana insists science offers the best explanation for the way in which humans fit into the world.
“We’re destroying that web of life that we’re intricately connected to. As those connections are breaking down, we’re putting humanity at risk,” he says.
Saldhana hopes that by understanding the ancestry we share with a variety of living beings, not just those who seem to look like us, will make it possible to better understand our multifaceted connections with the natural world. If we have a kinship with these creatures, he explains, then there’s an opportunity for a sense of responsibility for the fate of those relations. As the highest form of intelligent life, humans have a unique role and importance in the preservation of life, but that can’t happen as long as people don’t see and feel the need to protect those that can’t protect themselves against us.
|Posted by Kevin on June 28, 2012 at 12:35 AM||comments (0)|
For the second annual Ancestor's Trail hike, we were blessed with a perfect day for hiking. The day started off bright and beautiful and as the sun rose to it's zenith, clouds moved in to protect us from burning. A light drizzle cooled us off as we ended at Pinecliff park with Sam from Squamata showing off some of his reptilian wards.
Based on our experience last year, we decided to start the hike at Erindale Park where parking was plentiful but kept the rendezvous stations the same so we were hiking from the dawn of multicellular animal life forms (Metazoans) into the complexity of evolution that resulted in the splendour of the biodiversity we see around us today including the path we followed to humanity.
Registration was scheduled for 8:00am at Erindale park and we were pleased to welcome 12 youth volunteers from Volunteering Peel with their student leader co-ordinator. They helped with the check-in stations along the route where hikers passports were validated with stickers. After some instructions to the volunteers and participants, we set off on the Culham Trail at 8:45am. The new rendezvous posters proved to be a hit with their QR codes allowing not only the participants but others using the trail to access more information regarding our common ancestry with many representative species surviving today.
|Posted by Kevin on April 25, 2012 at 10:50 PM||comments (0)|
Exercise can make you smarter by helping to slow down and even turn around the physical decay of the brain. Writing in the New York Times Sunday magazine, Gretchen Reynolds (who writes the NYT’s Well blog) reviews some recent scientific studies exploring why walking, running, swimming and the like are good for your health and for your head.
Reynolds points out that the “brain, like all muscles and organs, is a tissue, and its function declines with underuse and age.” From our late 20s on, we lose about 1 percent of the volume of our hippocampus (which is associated with memory and certain types of learning) a year. In the 1990s, scientists discovered that adult human brains do generate new neurons and that exercise helps the brain to generate larger amounts of neurons. But just having more new neurons doesn’t alone increase intellect, Reynolds writes: For such to happen, the new brain cells have to join a neural network. Researchers found that, when mice were running, their brains “readily wired many new neurons into the neural network”; they observed the same when the mice were using their cognitive skills for such tasks as exploring new environments.
Another study cited by Reynolds also uses mice. Under psychology professor Justin S. Rhodes of the Beckman Institute for Advanced Science and Technology at the University of Illinois, researchers divided the mice into four groups:
One group lived in a world of sensual and gustatory plenty, dining on nuts, fruits and cheeses, their food occasionally dusted with cinnamon, all of it washed down with variously flavored waters. Their “beds” were colorful plastic igloos occupying one corner of the cage. Neon-hued balls, plastic tunnels, nibble-able blocks, mirrors and seesaws filled other parts of the cage. Group 2 had access to all of these pleasures, plus they had small disc-shaped running wheels in their cages. A third group’s cages held no embellishments, and they received standard, dull kibble. And the fourth group’s homes contained the running wheels but no other toys or treats.
The scientists had injected the mice with a substance that enabled them to track changes in their brain structure. Both groups of mice that had running wheels in their cages performed better on cognitive tests than the mice who did not and had healthier brains as a whole.
Scientists could hardly conduct such an experiment on humans due to ethical issues which are equally present in research using animal subjects — Rhodes’s study suggests that it is essential to provide mice in such situations with cognitive stimulation and to enable them to exercise. Exercise fosters an increase in the production of brain-derived neurotropic factor, or B.D.N.F., which “strengthens cells and axons, fortifies the connections among neurons and sparks neurogenesis.” Scientists can’t directly study similar effects in human brains, but they have found that B.D.N.F. levels are higher after people work out.
The exercise need not be all-out exhausting. In another study of 120 older men and women, some were assigned walking or stretching as exercise. Those who walked had larger hippocampi after a year.
Teachers (and parnets) know that physical activity and exercise can be key to helping students calm and focus better in the classroom. But the other benefit to exercise — and a compelling reason to preserve and promote physical education for elementary and secondary school students — is that it can help students do better in their academics. Even more, it can help all of us keep brains and bodies healthy in another affirmation of the ancient dictum, mens sana in corpore sano.
Read more: http://www.care2.com/causes/lets-take-a-walk-exercise-is-good-for-our-brains.html#ixzz1t6xmD4tA
|Posted by Kevin on July 6, 2011 at 12:15 AM||comments (0)|
The day turned out to be a beautiful one... just ordered up for our first Ancestor's Trail Hike on the Culham Trail in Mississauga. See pictures on http://www.ancestorstrail.ca/apps/photos
As it turns out, our event was graced by David J. Culham, honoured by the City in naming this beautiful urban trail after him. He served as Ward 6 Councillor. Also present was the sitting Ward 6 Councillor, Ron Starr, together with over 30 enthusiastic hikers who showed up to participate in this historic event. Historic, not because it was creating history... but honoring it by going back deep into our past... for the last billion years or so. Pilgrims were given passports to keep them informed of major events on the trail and to collect stickers and stamps proving their participation along the trail.
Mapped along the length of the Culham Trail to Erindale park, the 12.5k urban trail runs parallel to and criss-crossing the Credit River by means of pedestrian bridges affording a beautiful view of this soon-to-be-proclaimed Heritage River. We estimated the entire hike to take about 4 hours with stops along the way to discuss rendezvous points with common ancestors of living species of animals (with the exception of dinosaurs - with which we had a common ancestry going back 180 million years ago although they mostly went extinct 65 mya leaving birds as their only surviving decendents). The hike would end at the Erindale Park with a barbeque.
At the current calculation, we would have encountered our common ancestry with all known homo species (2 million years) within the parking lot of the Pinecliff Drive Park, homo sapiens (195,000 years) within one parking stall (10 ft) all known civilization (12,000 years) fitting into an average footprint (10") and the development of our current industrial society within the span of time (200 years) the width of a thumb (1")!
Each stride was calculated to take the pilgrims back 45,000-55,000 years (2' female - 2.5' male strides) covering the most recent 6 million years back to the first rendezvous with our common ancestor with Chimps and Bonobo apes in 80 metres or just over 100-115 strides. There we were met by a representative of the Jane Goodall Institute's Roots & Shoots youth leadership program, Abner Lico. He explained how Jane's work with Chimpanzees in the forests of Tanzania inspired her to create a lasting legacy in the Jane Goodall Institute and one of her most coveted initiatives to inspire our youth to develop programs to help promote environmental literacy, including saving our closest evolutionary cousins from exploitation.
The next (2) rendezvous, just a few strides further to 7 million years was with a common ancestor with Gorillas. Dian Fossey gave her life, literally, to the study of these great apes, also in the East African forests of Uganda and Rwanda.
It took another 7 million years to meet up with our next concestor with Orangutans (14mya) and then across the first foot bridge to meet up with Gibbons (18mya). Our next rendezvous with concestors of Old World Monkeys (25mya) and New World Monkeys (40mya) take place on the curve bordering the Credit River in River Run Park before leading off down the trail to meet up with Tarsiers (58mya), Lemurs (63mya) and Cologus (70mya). Rodents and Rabbits join (75mya) before the huge group of Laurasiatheres (75mya) which include most of the domestic and wild animals we are familar with today... and our first Passport Check Point off Sir Monty's Park.
|Posted by Kevin on March 19, 2011 at 8:46 AM||comments (0)|
By CARL ZIMMER
Published: March 14, 2011
Lurking in the blood of tropical snails is a single-celled creature called Capsaspora owczarzaki. This tentacled, amoebalike species is so obscure that no one even noticed it until 2002. And yet, in just a few years it has moved from anonymity to the scientific spotlight. It turns out to be one of the closest relatives to animals. As improbable as it might seem, our ancestors a billion years ago probably were a lot like Capsaspora.
The origin of animals was one of the most astonishing and important transformations in the history of life. From single-celled ancestors, they evolved into a riot of complexity and diversity. An estimated seven million species of animals live on earth today, ranging from tubeworms at the bottom of the ocean to elephants lumbering across the African savanna. Their bodies can total trillions of cells, which can develop into muscles, bones and hundreds of other kinds of tissues and cell types.
The dawn of the animal kingdom about 800 million years ago was also an ecological revolution.
Animals devoured the microbial mats that had dominated the oceans for more than two billion years and created their own habitats, like coral reefs.
The origin of animals is also one of the more mysterious episodes in the history of life. Changing from a single-celled organism to a trillion-cell collective demands a huge genetic overhaul. The intermediate species that might show how that transition took place have become extinct.
“We’re just missing the intervening steps,” said Nicole King, an evolutionary biologist at the University of California, Berkeley.
To understand how animals took on this peculiar way of life, scientists are gathering many lines of evidence. Some use rock hammers to push back the fossil record of animals by tens of millions of years. Others are finding chemical signatures of animals in ancient rocks. Still others are peering into the genomes of animals and their relatives like Capsaspora, to reconstruct the evolutionary tree of animals and their closest relatives. Surprisingly, they’ve found that a lot of the genetic equipment for building an animal was in place long before the animal kingdom even existed.
It was only in the past few years that scientists got a firm notion of what the closest relatives to animals actually are. In 2007, the National Human Genome Research Institute started an international project to compare DNA from different species and draw a family tree. The cousins of animals turn out to be a motley crew. Along with the snail-dwelling Capsaspora, our close relatives include choanoflagellates, amoebalike creatures that dwell in fresh water, where they hunt for bacteria.
Now scientists are trying to figure out how a single-celled organism like Capsaspora or choanoflagellates became a multicellular animal. Fortunately, they can get some hints from other cases in which microbes made the same transition. Plants and fungi evolved from single-celled ancestors, as well as dozens of other less familiar lineages, from brown algae seaweed to slime molds.
Primitive multicellularity may have been fairly easy to evolve. “All that has to happen is that the products of cell division stick together,” said Richard E. Michod of the University of Arizona. Once single-celled organisms shifted permanently to colonies, they could start specializing on different tasks. This division of labor made the colonies more efficient. They could grow faster than less specialized colonies.
Eventually, this division of labor could have led many cells in proto-animals to give up their ability to reproduce. Only a small group of cells still made the proteins required to produce offspring. The cells in the rest of the body could then focus on tasks like gathering food and fighting off disease.
“It’s not a hurdle,” said Bernd Schierwater of the University of Veterinary Medicine in Hanover, Germany. “It’s a very good way to be very efficient.”
Yet multicellularity also threw some new challenges at the ancestors of animals.
“When cells die in a group, they can poison each other,” said Dr. Michod. In animals, cells die in an orderly fashion, so that they release relatively few poisons. Instead, the dying cells can be recycled by their living brethren.
Another danger posed by multicellularity is the ability for a single cell to grow at the expense of others. Today that danger still looms large: cancer is the result of some cells refusing to play by the same rules as the other cells in our body.
Even simple multicellular organisms have evolved defenses to these cheaters. A group of green algae called volvox have evolved a limit to the number of times any cell can divide. “That helps reduce the potential for cells to become renegades,” said Dr. Michod.
To figure out the solutions that animals evolved, researchers are now sequencing the genomes of their single-celled relatives. They’re discovering a wealth of genes that were once thought to exist only in animals. Iñaki Ruiz-Trillo of the University of Barcelona and his colleagues searched Capsaspora’s genome for an important group of genes that encode proteins called transcription factors. Transcription factors switch other genes on and off, and some of them are vital for turning a fertilized egg into a complex animal body.
In the current issue of Molecular Biology and Evolution, Dr. Ruiz-Trillo and his colleagues report that Capsaspora shares a number of transcription factors that were once thought to be unique to animals. For example, they found a gene in Capsaspora that’s nearly identical to the animal gene brachyury. In humans and many other animal species, brachyury is essential for embryos to develop, marking a layer of cells that will become the skeleton and muscles.
Dr. Ruiz-Trillo and his colleagues have no idea what Capsaspora is doing with a brachyury gene. They’re now doing experiments to find out; in the meantime, Dr. Ruiz-Trillo speculates that single-celled relatives of animals use the brachyury gene, along with other transcription factors, to switch genes on for other tasks.
“They have to check out their environment,” said Dr. Ruiz-Trillo. “They have to mate with other organisms. They have to eat prey.”
Studies by other scientists point to the same conclusion: a lot of the genes once thought to be unique to the animal kingdom were present in the single-celled ancestors of animals. “The origin of animals depended on genes that were already in place,” Dr. King said.
In the transition to full-blown animals, Dr. King argues, these genes were co-opted for controlling a multicellular body. Old genes began to take on new functions, like producing the glue for sticking cells together and guarding against runaway cells that could become tumors.
Paleontologists have searched for decades for the fossils that chronicle this transition to the earliest animals.
Last year, Adam Maloof of Princeton and his colleagues published details of what they suggest are the oldest animal fossils yet found. The remains, found in Australia, date back 650 million years. They contain networks of pores inside of them, similar to the channels inside living sponges.
Sponges may have also left behind other ancient traces. Gordon Love of the University of California, Riverside, and his colleagues have drilled down into deposits of oil in Australia dating back at least 635 million years. In the stew of hydrocarbons they’ve brought up, they have found cholesterol-like molecules that are produced today only by one group of sponges.
The fact that sponges show up so early in the fossil record is probably no coincidence. Recent studies on animal genomes indicate that sponges are among the oldest lineages of living animals — if not the oldest. Sponges are also relatively simple compared with most other animals. They have no brains, stomachs or blood vessels.
Despite their seeming simplicity, sponges are card-carrying members of the animal kingdom. Like other animals, sponges can produce eggs and sperm, which can then produce embryos. Sponge larvae swim through the water to find their way to a good spot where they can settle down for a sedentary life and grow into adults. Their development is an exquisitely sophisticated process, with stem cells giving rise to several different cell types.
The first sponge genome was only published in August. It offered scientists an opportunity to compare the DNA of sponges to that of other animals as well as to Capsaspora and other single-celled relatives. The researchers looked at each gene in the sponge genome and tried to match it to related groups of genes in other species, known as gene families. All told, they were able to find 1,268 gene families shared by all animals — including sponges — but not by other species.
Those genes were presumably passed down to living animals from a common ancestor that lived 800 million years ago. And by surveying this catalog, scientists can infer some things about what that ancestor was like.
“It wasn’t just an amorphous blob of cells,” said Bernard M. Degnan of the University of Queensland. Instead, it was already setting aside eggs and sperm. It could produce embryos, and it could lay down complicated patterns in its body.
Animals didn’t just evolve multicellular bodies, however. They also appear to have evolved new ways of generating different kinds of bodies. Animals are more prone to mutations that shuffle sections of their proteins into new arrangements, a process called domain shuffling. “Domain shuffling seems to be a critical thing,” Dr. Degnan said.
Dr. Degnan and his colleagues have found another source of innovation in animals in a molecule called microRNA. When cells produce proteins from genes, they first make a copy of the gene in a molecule called RNA. But animal cells also make microRNAs that can attack RNA molecules and destroy them before they have a chance to make proteins. Thus they can act as another kind of switch to control gene activity.
MicroRNAs don’t seem to exist in single-celled relatives of animals. Sponges have eight microRNAs. Animals with more cell types that evolved later also evolved more microRNAs. Humans have 677, for example.
MicroRNAs and domain shuffling gave animals a powerful new source of versatility. They had the means to evolve new ways of reshaping their embryos to produce a wide range of forms — from big predators to burrowing mud-feeders.
That versatility may have allowed early animals to take advantage of changes that were unfolding all around them. About 700 million years ago, Earth emerged from the grips of a worldwide ice age. Noah Planavsky of the University of California, Riverside, and his colleagues have found evidence in rocks of that age for a sudden influx of phosphorus into the oceans at the same time. They speculate that as glaciers melted, phosphorus was washed from the exposed land into the sea.
The phosphorus may have acted as a pulse of fertilizer, stimulating algae growth. That may have been responsible for the rapid rise of oxygen in the ocean at the same time. Animals may have been prepared to use the extra oxygen to fuel large bodies and to use those bodies to devour other species.
“It was a niche to be occupied,” said Dr. Ruiz-Trillo, “and it was occupied as soon as the molecular machinery was in place.”
A version of this article appeared in print on March 15, 2011, on page D3 of the New York edition.