Navigation Links
Work of Field Museum scientist addresses question of chance in evolution
Date:6/9/2009

As Darwin observed, natural selection leading to adaptation of individuals and populations is occurring gradually and all the time. But over very long spans of time, the major channels of genetic organization, organism form, and the different ways organisms develop arose as outcomes of history-dependent variation that is now channeled, or constrained, within different groups of organisms. For example, most cats look like cats, develop like cats, but have a fossil record that begins from less than cat-like ancestors. So do snails, and crabs, and so on. But what if the broad evolutionary diversification of one of these groups were repeated by a few species in a single genus tens of millions of years after that initial diversification? What would that say about the roles of contingency, constraint, and adaptation? In other words, how big is the role of chance in the history of life?

An international team of researchers including Field Museum curator Scott Lidgard, PhD, has discovered a group of closely related living species that independently repeated the different step-like changes that occurred in the major diversification of their kind during the Cretaceous Period, roughly 100 to 90 million years ago. But this group of species arose 80 million years later!

The findings of Dr. Lidgard and his collaborators will be published online this week by the British journal, Proceedings of the Royal Society B. Dr. Lidgard's research focuses on cheilostome bryozoans, marine animal colonies whose bodies are made up of many genetically identical box-like individuals (zooids). In the simplest, most primitive cheilostomes, the soft feeding organ is squeezed out of the box by muscles pulling on a flexible membrane. The next step in diversification was calcified spines around the membrane, then fusion of the spines, then reduction of the fused spinal shield and membrane and invention of a water sac inside the box to provide enough volume to squeeze out the feeding organ. Lineages showing each of these stages are alive today. Then as now, these steps are seen as evolved defenses against small predators and parasites on the colony surface.

What is remarkable is that the molecular genealogy of the living species shows their origin only 15 million years ago, with the same trajectory as in the distant past! Evidence suggests that trajectory has occurred again and again in other groups. The authors argue that the original trajectory was highly contingent on a set of initial conditions, but that given the possibilities afforded by time, a genetic background would arise (like flipping a coin long enough to achieve 10 heads or tails in a row) that was visible to natural selection, most likely driven by predation. Acting together, the eventual realization of a particular genetic and developmental channel, and natural selection opened the way for an adaptive solution.


'/>"/>

Contact: Nancy O'Shea
noshea@fieldmuseum.org
312-665-7103
Field Museum
Source:Eurekalert

Related biology news :

1. First nanorust field test slated in Mexico
2. $1.6 million grant to lead development of resistance-detecting field kit
3. Field Museum paleontologist leads study on two new dinosaurs from China
4. Remembrance of things past influences how female field crickets select mates
5. Field stations foster serendipitous discoveries in environmental, biological sciences
6. Eugene-Springfield face Upper Willamette climate threats
7. New book expands field data available on orangutans
8. Satellites search out South Pole snowfields
9. Carnegies Field and Koshland Elected AAAS Fellows
10. Golf course: Playing fields, wildlife sanctuaries or both
11. Experts discuss applying systematic review to the field of nutrition
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:3/2/2017)... 2, 2017 Summary This report ... Merck KGaA and its partnering interests and activities since ... Description The Partnering Deals and Alliance since 2010 ... of one of the world,s leading life sciences companies. ... purchase to ensure inclusion of the most up to ...
(Date:2/28/2017)... 2017 News solutions for biometrics, bag drop ... ... 14 to 16 March, Materna will present its complete end-to-end ... travel is a real benefit for passengers. To accelerate the ... passenger touch point solutions to take passengers through the complete ...
(Date:2/22/2017)... LONDON , Feb. 22, 2017 ... by 2021, ABI Research identifies four technologies that ... solutions to secure significant share in the changing ... payments, and passive authentication.   "Companies ... it comes to security," says Dimitrios Pavlakis ...
Breaking Biology News(10 mins):
(Date:3/27/2017)... 27, 2017  Trovagene, Inc. (NASDAQ: TROV), a precision ... Officer, Bill Welch , will be presenting at ... 9:00 AM EDT at the Essex House in ... Chief Scientific Officer, Mark Erlander , Ph.D., will ... conference.   The presentation will be webcast live ...
(Date:3/27/2017)... 2017 Neurotrope, Inc. (OTCQB: NTRP),  a ... diseases, including Alzheimer,s disease, today announced that it ... the Company,s common stock on the NASDAQ Capital ... Market, a unit of the NASDAQ OMX Group. ... Opening Bell at the NASDAQ MarketSite in Times ...
(Date:3/24/2017)... and ROCKVILLE, Md. , ... company of Maxwell Biotech Venture Fund (MBVF), today announced ... SQ109 added to the standard drug therapy regimen in ... new small molecule drug discovered by scientists at Sequella, ... National Institutes of Health. A total ...
(Date:3/24/2017)... Ltd. ("Sinovac" or the "Company") (NASDAQ: SVA), a leading provider of ... its board of directors has amended its shareholder rights plan. The amendment ... to March 27, 2018. The amendment was not in response to any ... ... is a China -based biopharmaceutical company that focuses ...
Breaking Biology Technology: