Vaughan Grimes

Position

Associate Professor
Cross-appointed to Department of Earth Sciences
Associated Scientist (2009-) in the Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology

Academics

D.Phil. University of Bradford, UK, 2007
M.Sc. University of Bradford, UK, 2002
B.A. (Hons.) Memorial University of Newfoundland, 1998

Contact

Email: vgrimes@mun.ca
Phone: (709) 864-8861
Office: QC 2008

Research Interests

My research encompasses the fields of archaeological science, biomolecular archaeology and human skeletal biology. Specifically I focus on how culture, biological adaptations and climate change have influenced subsistence, settlement, migration and mobility patterns in the past. The primary analytical tool I use to address these issues is the analysis of stable and radiogenic isotopes (carbon, nitrogen, oxygen and strontium) from biological tissues (bone, teeth and hair), which are complemented by traditional morphologic-based methods of analyzing skeletal remains. Other areas of my research include the development of isotope-based analytical methodologies and unraveling the complex nature of isotopic and morphological variability within and between animal species.

For more information, please visit the Memorial Applied Archaeological Sciences webpage.

Student Resources

The Archaeology department has dedicated space for the chemical analysis of biological remains and comparative collections are available for osteoarchaeological research (read more on our facilities page).

Courses Taught

Undergraduate
ARCH 1000: Introduction to Archaeology and Bioarchaeology
ARCH 2430: Principles of Bioarchaeology
ARCH 2450: Principles of Archaeological Science
ARCH 2492: Forensic Archaeology
ARCH 2495: Archaeological Frauds, Myths and Mysteries (Online)
ARCH 3020: What is Human?
ARCH 3040: Human Osteology
ARCH 4041: Palaeopathology
ARCH 4043: Biomolecular Archaeology

Student supervision
Ph.D. Dissertations

Munkittrick, Jessica (in progress) Research topic: Regional insights into childhood lead exposure from historical North American skeletal remains.
Rand, Asta (in progress). Research topic: Prehispanic Maya Subsistence and Movement: Determining the Utility of Stable Sulphur Isotope Analysis.
Dussault, Frédéric (in progress). Research keywords: Precontact archaeology; environmental archaeology; palaeoecology; palaeoethnobotany; archaeoentomology; Dorset archaeology; historical ecology; hunter-gatherer archaeology. (Co-supervised with Dr. Trevor Bell)
Bower, Megan (2017). Exploring the Potential of Strontium Isotope Analysis to Detect Archaeological Migration Events in Southern Ontario, Canada.
Melo, Linda  (2012). Paleobiology, funerary practices and mobility of the Late Neolithic human remains exhumed from the funerary monuments of João da Horta 1 and 2. (Co-supervised with Dr. Ana-Maria Silva, University of Coimbra, Portugal).

M.A. Theses

Brydon, Rachelle (in progress). Research topic: tbd.
Merner, Courtney (in progress). Research topic: Investigating mobility using biogeochemistry at the Chalcolithic necropolis of Camino del Molino, Murcia, Spain.
Harris, Alison (2017). Stable Isotope Evidence for Amerindian Subsistence in Newfoundland.
Munkittrick, Jess (2016): A Nursery for Seamen: Life Histories from the St. John's Royal Naval Hospital Cemetery, Newfoundland.
Young-Boyle, Chandra (2016). Archaeological otoliths as environmental recorders: high resolution sampling of pacific cod (Gadus macrocephalus) otoliths from Kiska Island, Alaska.
Ellerbrok, Brittany (2014). Reconstructing the life history of individuals from a 17th century mass burial at Fortress Louisbourg using isotope analysis.
Pike, Kelly-Anne (2014). Bearing Identity: A Bicultural Analysis of Human Remains from Old Mission Point, New Brunswick. (Co-supervised with Dr. Michael Deal).
Guiry, Eric  (2012). Dogs as dietary analogues: assessing the cross-contextual validity of the canine surrogacy approach for stable isotope palaeodiet reconstructions.

B.A. Honours Essays

Conlan, Christine (in progress). Research topic: tbd.
Morry, Alicia (2017). The hunt for red ochre: potential applications of ochre characterization in Newfoundland and Labrador.
Rees, Daniel (2017). A possible case of Litterer-Siwe disease in the Maritime Archaic of the eastern sub-arctic: an analysis and retro-diagnosis using scanning electron microscopy.
Harris, Alison (2014). Distinguishing archaeological wild and domestic canids from Labrador, NL, Canada with stable carbon and nitrogen isotope analysis of bone collagen.
Dawe, Kendra (2012). Reconstructing diet of the Beothuk: a biomolecular pilot study.
Holmes, Andrew (2012). An Examination of Seasonal Temperature Variation During the Lower Magdalenian Period at El Miron Cave (Cantabria, Spain) Through the Use of Stable Isotope Analysis.
Desson, Rae (2011). An osteological study of human remains from the 17th century fishing plantation site of Dos de Cheval, Newfoundland.
Hill, Caitlyn (2009). ChAe-13, The Bay Bulls Burial: an osteological analysis and possible historical context of unidentified human remains.

Publications

Duggan, A.T., Harris, A.J.T., Marciniak, S., Marshall, I., Kuch, M., Kitchen, A., Renaud, G., Southon, J., Fuller, B., Young, J., Fiedel, S., Golding, G.B., Grimes, V., and Poinar, H. (2017) Genetic discontinuity between the Maritime Archaic and Beothuk populations in Newfoundland, Canada. Current Biology.  http://www.cell.com/current-biology/fulltext/S0960-9822(17)31091-6 [Open access]

Recent Press about this research:
The Guardian (UK): https://dd.org/10.1016/j.cub.2017.08.053
Globe and Mail: https://beta.theglobeandmail.com/news/national/dna-deepens-mystery-of-newfoundlandss-lost-beothuk-people/article36560469/?ref=http://www.theglobeandmail.com&
CBC: http://www.cbc.ca/news/canada/newfoundland-labrador/dna-study-beothuk-newfoundland-population-1.4351938

Madgwick, R., Lewis, J., Grimes, V., and Guest, P. (2017) On the hoof: exploring the supply of animals to the Roman legionary fortress at Caerleon using strontium (87Sr/86Sr) isotope analysis. Archaeological and Anthropological Sciences.https://doi.org/10.1007/s12520-017-0539-9

Gigleux, C., Grimes, V., Tütken, T., Knecht, R., and Britton, K. (2017) Reconstructing caribou seasonal biogeography in Little Ice Age (late Holocene) Western Alaska using intra-tooth strontium and oxygen isotope analysis. Journal of Archaeological Science: Reports. http://www.sciencedirect.com/science/article/pii/S2352409X1730425X
[Open access]

Faucher, A-M., Bain, A., and Grimes, V. (2017) First archaeological evidence for Old World crops in the Caribbean: the presence of barley on the island of Barbuda. Historical Archaeology. https://doi.org/10.1007/s41636-017-0059-6

Dussault, F., Bell, T.J., Grimes, V. (2016) Archaeoentomological perspectives on Dorset occupations in Newfoundland: A case study from the site of Phillip’s Garden (EeBi-1). Arctic 69(5):1-15.

Choudhury, S., Swanston, T., Varney, T., Cooper, D.M.L. George, G.N., Pickering, I.J. Grimes, V., Bewer, B., and Coulthard, I. (2016) Confocal X-Ray Fluorescence imaging facilitates high resolution elemental mapping in fragile archaeological bone. Archaeometry 58(S1):207-217.

Raghavan, M., Steinrücken, M., Harris, K., Schiffels, S., Rasmussen, S., DeGiorgio, M., … (48 authors)… Grimes, V., + 48 more. (2015) Genomic evidence for the Pleistocene and recent population history of Native Americans. Science 349(6250):aab3884-1 – aab3884-10.

Guiry, E.J., Staniforth, M., Nehlich, O., Grimes, V., Smith, C., Harpley, B., Noël, S., Richards, M. (2015) Tracing historical animal husbandry, meat trade, and food provisioning: A multi-isotopic approach to the analysis of shipwreck faunal remains from William Salthouse, Port Phillip, Australia. Journal of Archaeological Science: Reports 1:21-28.

Montgomery, J., Grimes, V., Buckberry, J., Evans, J.A., Richards, M.P., and Barrett, J.H. (2014) Finding Vikings with isotope analysis – the view from wet and windy islands. Journal of the North Atlantic 7 (sp7):54-70.

Raghavan, M., DeGiorgio, M., Albrechtsen, A., Moltke, I., Skoglund, P., Korneliussen, T., Gronnøw, B., Appelt, M., Christian Gulløv, H., Friesen, M., Fitzhugh, W., Malmström, H., Rasmussen, S., Olsen, J., Melchior, L., Fuller, B., Fahrni, S., Stafford Jr, T., Grimes, V., +37 more. The Genetic Prehistory of the New World Arctic. (2014) Science 345(6200):1255832-1–9.

Grimes, V., Fuller, B. and Guiry, E.J. (2014) Reconstructing the diets and origin of Norse occupation at Hrísbrú, Mosfell Valley, Iceland: the carbon, nitrogen and strontium isotope evidence. In Zori, D. and Byock J. (Eds.) Viking Archaeology in Iceland: The Mosfell Archaeological Project. pp. 105-116. Cursor Mundi 20.

Guiry, E.J., and Grimes, V. (2013) Domestic dog (Canis familiaris) diets among coastal Late Archaic groups of northeastern North America: A case study for the canine surrogacy approach. Journal of Anthropological Archaeology. 32:732-745.

Grimes, V., and Pellegrini, M. (2012) A comparison of pretreatment methods for the analysis of phosphate oxygen isotope ratios in bioapatite. Rapid Communications in Mass Spectrometry 27:375-390.

Guiry, E.J., Noël, S., Tourigny, E., and Grimes, V. (2012) A stable isotope method for identifying transatlantic origin of pig (Sus scrofa) remains at French and English fishing stations in Newfoundland. Journal of Archaeological Science, 39(7):2012-2022.

Richards, M.P., Grimes, V. and Blockley, S.M. (2012) Stable isotope analysis (C,N,O) of Lynford Quarry faunal samples. In Boisemeir, W., Coward F. and Gamble C. (Eds.) Neanderthals Among Mammoths: Excavations at Lynford Quarry, Norfolk. English Heritage.

Jay, M., Grimes, V. and Richards, M.P. (2012) Stable isotope analysis of animal bone from Pontnewydd Cave. In Aldhouse-Green, S., Peterson, R. and Walker, E. (Eds.). Neaderthals in Wales: Pontnewydd and the Elwy Valley Caves. 321-327. Cardiff, University of Wales Press.

Copeland, SR., Sponheimer, M., de Ruiter, DJ., Lee-Thorp, JA., Condron, D., le Roux, PJ., Grimes, V., Potze, S., Richards, MP. 2011. Strontium isotope evidence for landscape use by early hominin. Nature, 474:76-79.

Britton, K., Grimes, V., Niven, L., Steele, T., McPherron, S., Soressi, M., Kelly, T.E., Jaubert, J., Hublin, J.J., and Richards, M.P. 2011. Strontium isotope evidence for migration in late Pleistocene Rangifer: Implications for Neanderthal hunting strategies at the Middle Palaeolithic site of Jonzac, France. Journal of Human Evolution, 61:176-185.

Copeland, S.R., Sponheimer, M., Lee-Thorp, J.A., de Ruiter, D.J., le Roux, P.J., Grimes, V., Codron, D., Codron, J., Berger, L.R. and Richards, M.P. Using strontium isotopes to study site accumulation processes. Journal of Taphonomy 8(2-3):115-127.

Stallo, J. R., Shepartz, L.A., Grimes, V. and Richards, M.P. (2008) Strontium isotopes ratios and mobility reconstruction. In Amore, M.G. (Ed.) Necropolis of Apollonia. Tumulus 9. Tiranë: International Center for Albanian Archeology Monograph Series No. 2.

Richards, M., Grimes, V., Smith, C., Smith, T., Harvati, K., Hublin, J.J., Karkanas, P., and Panagopoulou, E. (2009) Response to Nowell and Horstwood (2009). Journal of Archaeological Science, 36:1657-1658

Briton, K., Grimes, V., Dau, J. and Richards, M.P. (2009) Reconstructing faunal mirgrations using intra-tooth sampling and strontium and oxygen isotope analyses: a case study of modern caribou (Rangifer tarandus granti). Journal of Archaeological Science, 36:1163-1172.

Copeland, S.R., Sponheimer, M., le Roux, P.J., Grimes, V., Lee-Throp, J.A., de Ruiter, D.J., and Richards, M.P. (2008) Strontium isotope ratios (87Sr/86Sr) of tooth enamel: a comparison of solution and laser ablation multicollector inductively coupled plasma mass spectrometry methods. Rapid Communications in Mass Spectrometry, 22:3187-3194.

Richards, M.P., Harvati, K., Grimes, V., Smith, C., Smith, T., Hublin, J. J., Karkanas, P., and Panagopoulou, E. (2008) Strontium isotope evidence of Neanderthal mobility at the site of Lakonis, Greece using laser-ablation PIMMS. Journal of Archaeological Sciences, 35:1251-1256.

Richards, M.P., Montgomery, J., Nehlich, O., and Grimes, V. (2008) Isotopic analysis of humans and animals from Vedrovice. Anthropologie: International Journal of the Science of Man, 46:185-194.

Wilson, A.S., Taylor, T., Ceruti, M.A., Chavez, J.A., Reinhard, J. Grimes, V., Meier-Augenstein, W., Cartmell, L., Stern, B., Richards, M.P., Worobey, M. Barnes, I., and Gilbert, T.P. (2007) Stable isotope and DNA evidence for ritual sequences in Inca child sacrifice. Proceedings of the National Academy of Sciences, 104(42):16456-16461.

Dobney, K., Jaques, D., Barrett, J., Johnstone, C., Carrott, J., Hall, A., Herman, J., Nichols, C., Müldner, G. and Grimes, V. (2007) Exploitation of resources and procurement strategies. In Dobney, K., Jaques, D., Barrett, J. and Johnstone, C. (Eds.) Farmers Monks & Aristocrats. The environmental archaeology of an Anglo-Saxon estate centre at Flixborough, North Lincolnshire, U.K. 190-212. Oxford: Oxbow/English Heritage.

Jay, M., Grimes, V., Montgomery, J., Lakin, K. and Evans, J. (2007) Multi-isotope analysis, Chapter 8: Environmental Evidence. pp. 351-354. In Brown, F., Howard-Davis, C., Evans, T., O’Connor, S., Spence, A., Heawood, R. and Lupton, A. (Eds.) The archaeology of the A1 (M) Darrington to Dishforth DBFO Road Scheme. Lancaster, Oxford Archaeology North.

Presentations (Selection)

Harris, A., Van Biesen, G., Duggan, A.T., Marciniak, S., Poinar, H., and Grimes, V. (2017) 7500 years by the sea: A compound specific isotope approach to aboriginal palaeodiet in Northeastern Canada.’ UK Archaeological Science Conference, 5-8 April, University College London, London, UK

Grimes, V., Harris, A., Duggan, A., Marciniak, S., and Poinar, H. (2017) Strontium and oxygen isotope evidence for Maritime Archaic mobility patterns at the site of Port au Choix-3, Newfoundland.’ 82nd Annual Meeting of the Society for American Archaeology, 29 March-2 April, Vancouver, Canada

Harris, A., Duggan, A.T., Marciniak, S., Poinar, H., and Grimes, V. (2017) Maritime Archaic subsistence in Newfoundland, Canada: Insights from d13C and d15N of bulk bone collagen and amino acids.’ 82nd Annual Meeting of the Society for American Archaeology, 29 March-2 April, Vancouver, Canada

Young-Boyle, C., Grimes, V., and Neville, V. (2016) Archaeological cod otoliths as environmental indicators: high resolution sampling of Pacific cod otoliths from Kiska Island, Alaska.’ 49th Annual Meeting of the Canadian Archaeological Association, 4-7 May, Whitehorse, YK, Canada

Grimes, V., Boaventura, R., Hillier, M., Silva, A-M., and Valera, A.C. (2016) Strontium isotope evidence for Late Neolithic mobility in South-Central Portugal.’ 81st Annual Meeting of the Society for American Archaeology, 6-10 April, Orlando, FL, USA

Munkittrick, J., Harris, A., Pike, K-A., and Grimes, V. (2016) They are one with the Tides of the Sea”: Diets of Settlers and Sailors in Newfoundland during the 17th to 19th centuries. 81st Annual Meeting of the Society for American Archaeology, 6-10 April, Orlando, FL, USA

Harris, A., Duggan, A.T., Marciniak, S., Poinar, H. and Grimes, V. (2016) Stable isotope evidence for precontact Amerindian diet in Newfoundland, Canada. 81st Annual Meeting of the Society for American Archaeology, 6-10 April, Orlando, FL, USA

Harris, A., Duggan, A.T., Marciniak, S., Marshall, I., Poinar, H. and Grimes, V. (2015) Dating the human occupation of Newfoundland and Labrador: Challenges and progress.’ 43rd Annual Meeting of the Canadian Association for Physical Anthropology, 28-31 October, Winnipeg, MA, Canada

Harris, A. and Grimes, V. (2015) Exploring human-canid interactions among the Dorset using carbon and nitrogen isotope analysis. 80th Annual Meeting of the Society for American Archaeology, 15-19 April, San Francisco, CA, USA

Munkittrick, J., and Grimes V. (2015) From cod to convoy: Dietary life histories from the St. John’s Naval hospital cemetery, NL. 47th Annual Meeting of the Canadian Archaeological Association, 29 April – 2 May, St. John’s, NL, Canada

Dussault, F., Bell, T., and Grimes, V. (2015) Archaeoentomological perspectives on Dorset occupations in Newfoundland: preliminary results from Phillip’s Garden (EeBi-1) and Stock Cove (CkAl-3).’ 47th Annual Meeting of the Canadian Archaeological Association, 29 April – 2 May, St. John’s, NL, Canada

Grimes, V. (2015) Tooth chemistry and migration events in archaeology: from hominins to Vikings’ McMaster University Anthropology Colloquium Series, 24 March, Hamilton, Ontario, Canada

Harris, A, Marshall, I., Jerkic, S., Poinar, H. and Grimes, V. (2014) A population on the run: Investigating the Beothuk population collapse using stable carbon and nitrogen isotope analysis of human bone collagen. 42nd Annual Meeting of the Canadian Association for Physical Anthropology, 6-8 November, Fredericton, NB, Canada

Munkittrick, J. and Grimes, V. (2014) Diet and geographic origins of British Royal Navy sailors: Life histories from the Southside Naval Hospital cemetery, St. John’s, NL. 42nd Annual Meeting of the Canadian Association for Physical Anthropology, 6-8 November, Fredericton, NB, Canada

Bower, M. and Grimes, V. (2014) Investigating the Potential of Strontium Isotope Analysis to Detect Archaeological Migration Events in Southern Ontario. 47th Annual Meeting of the Canadian Archaeological Association, 14-18 May, London, ONT, Canada

Grimes, V. and Fuller, B.T. (2014) Building a new chronology for prehistoric human occupations in Atlantic Canada. Radiocarbon and Diet: aquatic food resources and reservoir effects, 24-26 September, Kiel, Germany

Grimes, V. (2013) The Basques of ‘Butus’: life at a 16th century whaling enterprise in the New World. UK Archaeological Science Conference, 11-14 April, Cardiff, Wales, UK.

Grimes, V., Fuller, B.T., Fahrni, S.M., Guiry, E. and Smith, C. (2013) Re-dating the oldest burial mound in North America: the challenges of archaeological conservation for radiocarbon dating bone. UK Archaeological Science Conference, 11-14 April, Cardiff, Wales, UK.

Guiry, E.J., Smith, C., Salazar-García, D.C. and Grimes, V. (2013) Dogs as dietary proxies for humans in the Spanish Copper Age: A case study using bulk and compound specific stable carbon isotope analyses. 78th Annual Meeting of the Society for American Archaeology, 3-7 April, Honolulu, Hawaii, USA

Guiry, E.J., Grimes, V., Smith, C., Noël, S. and Touriqny, E. (2012) Integrating bone chemistry and faunal analyses in historical archaeology: A review and case study from Newfoundland. 2012 Council for Northeast Historical Archaeology, 4-7 October, St. John’s, NL, Canada

Guiry, E.J., Noël, S., Dupont-Hébert, C. and Grimes, V. (2012) Understanding Meat Provisioning Practices among Historic North Atlantic Fisheries: Insights from Stable Isotope Analyses. 45th Annual Meeting of the Canadian Archaeological Association, 16-20 May, Montreal, Canada.

Guiry, E.J., Touriqny, E., Noël, S. and Grimes, V. (2012) Meat Provisioning in Colonial Fishing Stations: Integrating Zooarchaeology and Stable Isotope Analysis.’ La Trobe University Archaeology Postgraduate Conference, 16 March, Melbourne, Australia.

Grimes, V., Dawe, K., Poinar, H., Younghusband, B. and Marshall, I. (2011) Re-assessing the human occupation of Eastern Canada: diets and dates. UK Archaeological Sciences Conference, 15-18 September, Reading University. Reading, UK.

Guiry, E.J., Touriqny, E., Noël, S. and Grimes, V. (2011) Animal husbandry in New World colonial fishing stations: insights from stable isotope analysis.’ UK Archaeological Science Conference, 15-18 September, Reading University, Reading, UK.

Grimes, V. and Dawe, K. (2011) Biomolecular study into the lifeways and genetics of prehistoric people from Newfoundland and Labrador.’ Canadian Archaeology Association, Annual Meeting, 19-21 May, Halifax, Canada.

Copeland, S., Richards, M.P., Lee-Thorp, J.A., Neveling, J. Grimes, V. and Grine, F.E. (2010) Isotopic evidence for the geographic origins and diet of the 36,000 year-old-Hofmyer skull. American Association of Physical Anthropologists, 79th Annual Meeting, 14-17 April, Albuquerque, New Mexico, USA.

Verna, C., Grimes, V., Toussaint, M., Hublin, J.-J. and Richards, M.P. (2010) Tracing Neanderthal movement and mobility using strontium isotope analysis: case studies from Belgium.’ Paleoanthropology Society, 2010 Annual Meeting, 13-14 April, St. Louis, Missouri, USA.

Grimes, V., Copeland, S.R., le Roux, P., Sponheimer, M., Lee-Thorp, J., de Ruiter, D. and Richards, M.P. (2008) Recent developments in micro-sampling techniques of modern and archaeological dental tissues for strontium isotope ratios.’ Canadian Association for Physical Anthropology, 5-8 November, Hamilton, Canada.

Research Funding and Grants

2014-2017 A biomolecular archaeology study of prehistoric North Americans from Newfoundland and Labrador. SSHRC Insight Grant (Role: Co-PI with Hendrik Poinar, McMaster University).

2014-2018 Investigating lead exposure patterns in Royal Navy populations from the colonial era.’ SSHRC Insight Grant (Role: Co-PI with T. Varney, Lakehead University; D. Cooper and I. Coulthard, University of Saskatchewan).

2013-2017 Understanding cultural resilience and climate change on the Bering Sea through Yup’ik Ecological Knowledge, Lifeways, Learning and Archaeology (ELLA)’ AHRC Research Grant – 4 years. (Role: Collaborator with PI Richard Knecht, Co-investigator Kate Britton, and Co-investigator Charlotta Hillerdal, University of Aberdeen, UK).

2013 A biomolecular archaeology study of prehistoric Native North Americans from Newfoundland and Labrador.’ Memorial University Office of Research Grant. (Role: PI)

2012 Compositional and isotopic characterization of complex organic mixture for the study of origin and preservation of hydrocarbons and biomarkers. Canada Foundation for Innovation – Leaders Opportunity Fund and Research and Development Corporation – Leverage R&D Program, Government of Newfoundland and Labrador (Role: Co-PI with Penny Morrill, Department of Earth Sciences, MUN).

2012-2016 The Dorset Palaeoeskimo site of Phillip's Garden, northwestern Newfoundland: late phase occupation and site abandonment.’ SSHRC Insight Grant. (Role: Co-PI with M.A.P. Renouf and P. Wells, Department of Archaeology, MUN)

2012 Developing a new chronology for prehistoric human occupations of Newfoundland and Labrador.’ Memorial University Arts Research Initiative. (Role: PI)

2010 Establishment of the Memorial University biomolecular archaeology research group facility. Research and Development Corporation - IRIF program, Government of Newfoundland and Labrador. (Role: PI)

2009 Reconstructing diet and migration of the Beothuk: a multi-isotope biogeochemical pilot study. Provincial Archaeology Office and Community Economic Development Program, Government of Newfoundland and Labrador. (Role: PI)

Contact

Department of Archaeology

230 Elizabeth Ave

St. John's, NL A1B 3X9 CANADA

Tel: (709) 864-2530

Fax: (709) 864-2552

becomestudent@mun.ca